add source for exercise-02
This commit is contained in:
Andrew Straw
parent
8bb7bdbab6
commit
7886098144
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{
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"cells": [
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{
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"cell_type": "markdown",
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"metadata": {
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"nbgrader": {
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"grade": false,
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"grade_id": "cell-d3917cf691ff056c",
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"locked": true,
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"schema_version": 3,
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"solution": false,
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"task": false
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}
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},
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"source": [
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"# Python Basics - Variables and Functions"
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]
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},
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{
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"cell_type": "code",
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"execution_count": null,
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"metadata": {
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"nbgrader": {
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"grade": false,
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"grade_id": "cell-4367d53c03c57930",
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"locked": true,
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"schema_version": 3,
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"solution": false,
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"task": false
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}
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},
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"outputs": [],
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"source": [
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"# You must run this cell, but you can ignore its contents.\n",
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"\n",
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"import hashlib\n",
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"\n",
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"def ads_hash(ty):\n",
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" \"\"\"Return a unique string for input\"\"\"\n",
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" ty_str = str(ty).encode()\n",
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" m = hashlib.sha256()\n",
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" m.update(ty_str)\n",
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" return m.hexdigest()[:10]"
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]
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},
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{
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"cell_type": "markdown",
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"metadata": {
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"nbgrader": {
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"grade": false,
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"grade_id": "cell-a396e1b67f65db5a",
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"locked": true,
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"schema_version": 3,
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"solution": false,
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"task": false
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}
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},
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"source": [
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"## Problem 1 - variable assignment\n",
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"\n",
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"Assign a value of 42 to the variable named `x`."
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]
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},
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{
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"cell_type": "code",
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"execution_count": null,
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"metadata": {
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"nbgrader": {
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"grade": false,
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"grade_id": "cell-ae28d599cff14ed6",
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"locked": false,
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"schema_version": 3,
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"solution": true,
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"task": false
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}
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},
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"outputs": [],
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"source": [
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"x=42"
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]
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},
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{
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"cell_type": "code",
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"execution_count": null,
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"metadata": {
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"nbgrader": {
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"grade": true,
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"grade_id": "cell-0e037ae0dbd9b1ad",
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"locked": true,
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"points": 1,
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"schema_version": 3,
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"solution": false,
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"task": false
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}
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},
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"outputs": [],
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"source": [
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"# This checks that the above worked\n",
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"assert ads_hash(x)=='73475cb40a'"
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]
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},
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{
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"cell_type": "markdown",
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"metadata": {
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"nbgrader": {
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"grade": false,
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"grade_id": "cell-c4b55ac9cdc77304",
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"locked": true,
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"schema_version": 3,
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"solution": false,
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"task": false
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}
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},
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"source": [
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"## Problem 2 - solving exceptions\n",
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"\n",
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"Modify the following so that it runs without an \"exception\" (an error in Python):\n",
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"\n",
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"\n",
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"```python\n",
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"y = 2 plus 2\n",
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"```"
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]
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},
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{
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"cell_type": "code",
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"execution_count": null,
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"metadata": {
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"nbgrader": {
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"grade": false,
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"grade_id": "cell-c4b1b65a81fbe0ae",
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"locked": false,
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"schema_version": 3,
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"solution": true,
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"task": false
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}
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},
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"outputs": [],
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"source": [
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"y=2+2"
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]
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},
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{
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"cell_type": "code",
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"execution_count": null,
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"metadata": {
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"nbgrader": {
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"grade": true,
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"grade_id": "cell-f25ca0617c9fefdf",
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"locked": true,
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"points": 1,
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"schema_version": 3,
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"solution": false,
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"task": false
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}
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},
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"outputs": [],
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"source": [
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"# This checks that the above worked\n",
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"assert ads_hash(y)=='4b227777d4'"
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]
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},
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{
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"cell_type": "markdown",
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"metadata": {
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"nbgrader": {
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"grade": false,
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"grade_id": "cell-d2ec8851f4e990e5",
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"locked": true,
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"schema_version": 3,
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"solution": false,
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"task": false
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}
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},
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"source": [
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"## Problem 3 - using the Python Tutor\n",
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"\n",
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"Run the following code at the [Python Tutor](http://pythontutor.com/).\n",
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"\n",
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"1. Click on \"Visualize your code and get live help now\" in the Python Tutor website.\n",
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"2. Copy this code into your clipboard:\n",
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"```python\n",
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"x = 42\n",
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"y = x + 42\n",
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"```\n",
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"3. Paste it into the edit window of the Python Tutor.\n",
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"4. Click the \"Visualize Execution\" button of the Python Tutor.\n",
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"5. Click the \"Next button\" until all steps are done.\n",
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"\n",
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"**For great insight, run all the problems in this exercise in the Python Tutor and carefully watch what is happening. This will be a massive help for you understand what your programs are doing**\n",
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"\n",
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"How many variables are in the global frame? Assign the answer to the variable named `answer`."
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]
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},
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{
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"cell_type": "code",
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"execution_count": null,
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"metadata": {
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"nbgrader": {
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"grade": false,
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"grade_id": "cell-c90583224070d298",
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"locked": false,
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"schema_version": 3,
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"solution": true,
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"task": false
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}
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},
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"outputs": [],
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"source": [
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"answer=2"
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]
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},
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{
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"cell_type": "code",
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"execution_count": null,
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"metadata": {
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"nbgrader": {
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"grade": true,
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"grade_id": "cell-4a36c43c001f4d04",
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"locked": true,
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"points": 1,
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"schema_version": 3,
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"solution": false,
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"task": false
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}
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},
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"outputs": [],
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"source": [
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"# This checks that the above worked\n",
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"assert ads_hash(answer)=='d4735e3a26'"
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]
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},
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{
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"cell_type": "markdown",
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"metadata": {
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"nbgrader": {
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"grade": false,
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"grade_id": "cell-a8185ffe231c0ce4",
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"locked": true,
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"schema_version": 3,
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"solution": false,
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"task": false
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}
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},
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"source": [
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"## Problem 4 - functions\n",
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"\n",
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"Here is an example function named `double` that has one input named `x` and returns `x*2` (`x` times two).\n",
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"\n",
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"```python\n",
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"def double(x):\n",
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" return x*2\n",
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"```\n",
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"\n",
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"Remember that all functions in python are defined with the `def` word, then the name of the function, then zero, one, two, or more arguments in parentheses, then a colon. The body of the function must be in a block - a group of lines with the same indentation.\n",
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"\n",
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"Now, make a function named `triple` that has one input named `x` and returns `x*3`."
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]
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},
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{
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"cell_type": "code",
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"execution_count": null,
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"metadata": {
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"nbgrader": {
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"grade": false,
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"grade_id": "cell-69c4b1cf7dfd376f",
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"locked": false,
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"schema_version": 3,
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"solution": true,
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"task": false
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}
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},
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"outputs": [],
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"source": [
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"def triple(x):\n",
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" return x*3"
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]
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},
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{
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"cell_type": "code",
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"execution_count": null,
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"metadata": {
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"nbgrader": {
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"grade": true,
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"grade_id": "cell-c2eb28444382a954",
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"locked": true,
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"points": 1,
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"schema_version": 3,
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"solution": false,
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"task": false
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}
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},
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"outputs": [],
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"source": [
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"# This checks that the above worked\n",
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"assert ads_hash(triple(3))=='19581e27de' \n",
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"assert ads_hash(triple(4))=='6b51d431df'\n",
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"assert ads_hash(triple(5))=='e629fa6598'"
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]
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},
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{
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"cell_type": "markdown",
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"metadata": {
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"nbgrader": {
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"grade": false,
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"grade_id": "cell-5c7cd3a6ef33c261",
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"locked": true,
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"schema_version": 3,
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"solution": false,
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"task": false
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}
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},
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"source": [
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"## Problem 5 - functions with multiple arguments\n",
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"\n",
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"Here is an example function named `my_func` that takes two inputs, `x` and `y` and does a bit of math on the inputs:\n",
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"\n",
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"```python\n",
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"def my_func(x,y):\n",
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" return x + 2*y\n",
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"```\n",
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"\n",
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"Make a function named `foo` which returns five times the first argument plus three times the second argument."
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]
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},
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{
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"cell_type": "code",
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"execution_count": null,
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"metadata": {
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"nbgrader": {
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"grade": false,
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"grade_id": "cell-a7218905d3eb7d0d",
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"locked": false,
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"schema_version": 3,
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"solution": true,
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"task": false
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}
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},
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"outputs": [],
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"source": [
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"# Write your answer here\n",
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"def foo(a,b):\n",
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" return 5*a + 3*b"
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]
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},
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{
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"cell_type": "code",
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"execution_count": null,
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"metadata": {
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"nbgrader": {
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"grade": true,
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"grade_id": "cell-a417fcd5f3319f27",
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"locked": true,
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"points": 1,
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"schema_version": 3,
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"solution": false,
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"task": false
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}
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},
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"outputs": [],
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"source": [
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"# This checks that the above worked\n",
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"assert ads_hash(foo(3,10))=='811786ad1a'\n",
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"assert ads_hash(foo(10,3))=='3e1e967e9b'\n",
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"assert ads_hash(foo(13,2302))=='5f7635b6a1'"
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]
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},
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{
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"cell_type": "markdown",
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"metadata": {
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"nbgrader": {
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"grade": false,
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"grade_id": "cell-8f0143cd8208922f",
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"locked": true,
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"schema_version": 3,
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"solution": false,
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"task": false
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}
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},
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"source": [
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"## Problem 6 - calling functions from functions\n",
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"\n",
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"We can call functions from within functions.\n",
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"\n",
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"Here are two example functions named `double` and `double_twice`\n",
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"\n",
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"```python\n",
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"def double(x):\n",
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" return x*2\n",
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"\n",
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"def double_twice(x):\n",
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" y = double(x)\n",
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" z = double(y)\n",
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" return z\n",
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"```\n",
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"\n",
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"Re-use your function `triple` from above and make a function named `triple_thrice` which calls `triple` three times repeatedly on its input value."
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]
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},
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{
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"cell_type": "code",
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"execution_count": null,
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"metadata": {
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"nbgrader": {
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"grade": false,
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"grade_id": "cell-aa0cfdb16d440f6b",
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"locked": false,
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"schema_version": 3,
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"solution": true,
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"task": false
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}
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},
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"outputs": [],
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"source": [
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"def triple_thrice(x):\n",
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" return triple(triple(triple(x)))"
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]
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},
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{
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"cell_type": "code",
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"execution_count": null,
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"metadata": {
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"nbgrader": {
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"grade": true,
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"grade_id": "cell-ee28ca6d0fc146ee",
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"locked": true,
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"points": 1,
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"schema_version": 3,
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"solution": false,
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"task": false
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}
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},
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"outputs": [],
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"source": [
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"assert ads_hash(triple_thrice(3))=='5316ca1c5d'\n",
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"assert ads_hash(triple_thrice(4))=='9537f32ec7'"
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]
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},
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{
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"cell_type": "markdown",
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"metadata": {
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"nbgrader": {
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"grade": false,
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"grade_id": "cell-66fac9b6dafd5cd6",
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"locked": true,
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"schema_version": 3,
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"solution": false,
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"task": false
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}
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},
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"source": [
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"## Problem 7 - variable scopes\n",
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"\n",
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"Functions are also useful because they let you \"hide\" variables so they do not \"pollute\" other parts of your code. In other words, functions let you make modular pieces of code which do not affect each other.\n",
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"\n",
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"Consider this piece of code, and think about the value of `x` throughout the code.\n",
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"\n",
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"```python\n",
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"x = 43\n",
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"\n",
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"def blah(x):\n",
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" x = x - 26\n",
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" return x\n",
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"\n",
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"blah(2)\n",
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"\n",
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"x\n",
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"```\n",
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"\n",
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"In the very last line, what is the value of `x`?\n",
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"\n",
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"In the very last line, `x` has a value of `43`. However, inside the function there is a *local* variable, also named `x`, which can have a different value. Changes to this local variable `x` in the function do not affect the `x` in the *global frame*. (This could also be called the *global scope*. \"Frame\" and \"scope\" are synonyms.)\n",
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"\n",
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"Inside a function, variable from the outside frame can be *read* if there is no local variable in the function with the same name. Consider this code. Here we will read the variable `x` inside the function because we have no argument or other local variable named `x`.\n",
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"\n",
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"```python\n",
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"x = 43\n",
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"\n",
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"def blah(y):\n",
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" z = x - y\n",
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" return z\n",
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"\n",
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"q = blah(2)\n",
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"```\n",
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"\n",
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"What is the value of `q`?\n",
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"\n",
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"The value of `q` here will be 41.\n",
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"\n",
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"*Advanced*: Frames can be nested - for example if you call a function named `function2` from another function named `function1`, the frame of `function2` will be created while the frame of `function1` continues to exist.\n",
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"\n",
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"In this second example, `y` is defined only inside the function. What is it's value in the function? Assign your answer to the variable `y`."
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]
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},
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{
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"cell_type": "code",
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"execution_count": null,
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"metadata": {
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||||
"nbgrader": {
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"grade": false,
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||||
"grade_id": "cell-cdc1a3f2940f028c",
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"locked": false,
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||||
"schema_version": 3,
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"solution": true,
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"task": false
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||||
}
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},
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"outputs": [],
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"source": [
|
||||
"y=2"
|
||||
]
|
||||
},
|
||||
{
|
||||
"cell_type": "code",
|
||||
"execution_count": null,
|
||||
"metadata": {
|
||||
"nbgrader": {
|
||||
"grade": true,
|
||||
"grade_id": "cell-93d460ecce09dcfd",
|
||||
"locked": true,
|
||||
"points": 1,
|
||||
"schema_version": 3,
|
||||
"solution": false,
|
||||
"task": false
|
||||
}
|
||||
},
|
||||
"outputs": [],
|
||||
"source": [
|
||||
"assert ads_hash(y)=='d4735e3a26'"
|
||||
]
|
||||
},
|
||||
{
|
||||
"cell_type": "markdown",
|
||||
"metadata": {
|
||||
"nbgrader": {
|
||||
"grade": false,
|
||||
"grade_id": "cell-56a56e248a2320f1",
|
||||
"locked": true,
|
||||
"schema_version": 3,
|
||||
"solution": false,
|
||||
"task": false
|
||||
}
|
||||
},
|
||||
"source": [
|
||||
"## Problem 8 - return values of functions\n",
|
||||
"\n",
|
||||
"To return a value, a function must use the keyword `return`. Otherwise, the special python type `None` is returned. Check these two functions out:\n",
|
||||
"\n",
|
||||
"```python\n",
|
||||
"def func_one(x):\n",
|
||||
" return x*10\n",
|
||||
"\n",
|
||||
"def func_two(x):\n",
|
||||
" x*10\n",
|
||||
"```\n",
|
||||
"\n",
|
||||
"What is the result of `func_one(10)`? It is `100`. What is the result of `func_two(10)`? It is `None`, a special type in Python which means \"nothing\".\n",
|
||||
"\n",
|
||||
"Taking this as a starting point, fix the `my_triple` function so that it returns the value of `x*3`.\n",
|
||||
"\n",
|
||||
"```\n",
|
||||
"def my_triple(x):\n",
|
||||
" x*3\n",
|
||||
"```"
|
||||
]
|
||||
},
|
||||
{
|
||||
"cell_type": "code",
|
||||
"execution_count": null,
|
||||
"metadata": {
|
||||
"nbgrader": {
|
||||
"grade": false,
|
||||
"grade_id": "cell-3d76a38f83df69ce",
|
||||
"locked": false,
|
||||
"schema_version": 3,
|
||||
"solution": true,
|
||||
"task": false
|
||||
}
|
||||
},
|
||||
"outputs": [],
|
||||
"source": [
|
||||
"def my_triple(x):\n",
|
||||
" return x*3"
|
||||
]
|
||||
},
|
||||
{
|
||||
"cell_type": "code",
|
||||
"execution_count": null,
|
||||
"metadata": {
|
||||
"nbgrader": {
|
||||
"grade": true,
|
||||
"grade_id": "cell-f70296c24b543ae5",
|
||||
"locked": true,
|
||||
"points": 1,
|
||||
"schema_version": 3,
|
||||
"solution": false,
|
||||
"task": false
|
||||
}
|
||||
},
|
||||
"outputs": [],
|
||||
"source": [
|
||||
"assert ads_hash(my_triple(100))=='983bd614bb'"
|
||||
]
|
||||
},
|
||||
{
|
||||
"cell_type": "markdown",
|
||||
"metadata": {
|
||||
"nbgrader": {
|
||||
"grade": false,
|
||||
"grade_id": "cell-0748880c1c3a5b6f",
|
||||
"locked": true,
|
||||
"schema_version": 3,
|
||||
"solution": false,
|
||||
"task": false
|
||||
}
|
||||
},
|
||||
"source": [
|
||||
"## Problem 9 - `print()` is not return\n",
|
||||
"\n",
|
||||
"One thing that can be confusing is the difference between the return value of a cell in Jupyter notebook - which gets displayed automatically and the use of the built-in `print()` function.\n",
|
||||
"\n",
|
||||
"```python\n",
|
||||
"print(1234)\n",
|
||||
"```\n",
|
||||
"\n",
|
||||
"Will print `1234` but has no return value. This can be tricky in functions.\n",
|
||||
"\n",
|
||||
"Consider this function\n",
|
||||
"\n",
|
||||
"```python\n",
|
||||
"def my_great_function(a):\n",
|
||||
" print(a*30)\n",
|
||||
"```\n",
|
||||
"\n",
|
||||
"What does this function return?\n",
|
||||
"\n",
|
||||
"It returns `None`.\n",
|
||||
"\n",
|
||||
"Now make a function called `my_even_better_function` which returns the value of its input times thirty."
|
||||
]
|
||||
},
|
||||
{
|
||||
"cell_type": "code",
|
||||
"execution_count": null,
|
||||
"metadata": {
|
||||
"nbgrader": {
|
||||
"grade": false,
|
||||
"grade_id": "cell-25d97b85b08d5a2c",
|
||||
"locked": false,
|
||||
"schema_version": 3,
|
||||
"solution": true,
|
||||
"task": false
|
||||
}
|
||||
},
|
||||
"outputs": [],
|
||||
"source": [
|
||||
"def my_even_better_function(a):\n",
|
||||
" return a*30"
|
||||
]
|
||||
},
|
||||
{
|
||||
"cell_type": "code",
|
||||
"execution_count": null,
|
||||
"metadata": {
|
||||
"nbgrader": {
|
||||
"grade": true,
|
||||
"grade_id": "cell-b2fc619e60513768",
|
||||
"locked": true,
|
||||
"points": 1,
|
||||
"schema_version": 3,
|
||||
"solution": false,
|
||||
"task": false
|
||||
},
|
||||
"tags": []
|
||||
},
|
||||
"outputs": [],
|
||||
"source": [
|
||||
"assert ads_hash(my_even_better_function(32))=='7f5642cd0c'"
|
||||
]
|
||||
}
|
||||
],
|
||||
"metadata": {
|
||||
"celltoolbar": "Create Assignment",
|
||||
"kernelspec": {
|
||||
"display_name": "Python 3 (ipykernel)",
|
||||
"language": "python",
|
||||
"name": "python3"
|
||||
},
|
||||
"language_info": {
|
||||
"codemirror_mode": {
|
||||
"name": "ipython",
|
||||
"version": 3
|
||||
},
|
||||
"file_extension": ".py",
|
||||
"mimetype": "text/x-python",
|
||||
"name": "python",
|
||||
"nbconvert_exporter": "python",
|
||||
"pygments_lexer": "ipython3",
|
||||
"version": "3.11.8"
|
||||
}
|
||||
},
|
||||
"nbformat": 4,
|
||||
"nbformat_minor": 4
|
||||
}
|
||||
Loading…
Reference in a new issue