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Intro to Python: Labs

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Sam Moorhouse edited this page Jun 20, 2017 · 29 revisions

Intro to Python: Labs

Welcome to the Python lab! Work through this sheet in pairs, making sure that you understand each bit of code before you move on.

If you get something wrong, let us know! Other people may have done the same thing; maybe you can help them.

1: Basics

Try the following in the Python REPL. What do they do?

  • print "hello"
  • print 'hello'
  • print hello

Let's do some maths!

  • 4 + 5
  • 8 * 3
  • 4 / 3
  • 4.0 / 3
  • 3 + 5 * 9

Adding Strings?

  • "abc" + "def"
  • "hello" + " " + "world"
  • "123" + "5"

Variables!

  • first = "hello"
  • second = "world"
  • first + " " + second
  • type(first)

User input?

  • name = raw_input("What is your name?")
  • type(name)
  • age = int(raw_input("What is your age?"))
  • type(age)

2: Functions

In a file called person.py:

  • Write a function called get_age that asks the user for their age, and returns it as an int
  • Write another function called get_name, which does the same but for the users age
  • Call both these functions and tell the user what you know about them!

3: Loops

In a file called while_loop.py, write the following code:

i = 0
while(i < 10):
    i = i + 1
    print i
  • Explain what's happening. Can you print the numbers from 7 to 19?
  • Can you print all the even numbers between 12 and 20?
  • Write a function called evens that takes two numbers and prints all the even numbers between them.
  • Write another function, reverse_evens, that does the same but prints the numbers in reverse.

In a file called for_loop.py, write the following code:

for i in range(1,11):
    print i
  • Explain what's happening. What is i? What is range?

Type the following code:

for j in [1, 2, 3]:
    print j
  • Explain what's happening. How can you use range to do the same thing?
  • What's the type of [1, 2, 3]? What type of data does range return?

4: If

In a file called conditional.py, write the following code:

i = 8
if(i % 2):
    print "Odd Number"
else:
    print "Even Number"
  • What is %? What is i % 2?
  • Write a function called evens that takes a list of numbers and returns the sum of all the even numbers
  • Copy your function that asks for a persons age. Tell them if you think they're old or not!
  • Write a function that asks the user for the year they were born, then calculates roughly how old they are.
  • Find out the definition of a leap year. Write a function that asks the user the year they were born, and then tells them if that year was a leap year.

5: Tuples

In the file tuples.py, write two functions:

  • partition should take a number and return a 2-tuple, with the number on the left if it's even, and on the right if it's odd. The other slot should be filled with the constant None
  • partition_list, which takes a list of numbers and returns a 2-tuple of lists. It should use your partition function to split the input list into the odd numbers and the even numbers.

Stretch

Well done if you've come so far. Below are some harder labs that will take more time. Everyone should hopefully get at least this far :)

Stretch: Roman Numerals

Write a function that takes a number and prints out its value in Roman Numerals

e.g. 3 = III, 56 = LVI etc...

Stretch: Complex numbers

Investigate the complex numeric type. In a file called mandelbrot.py, write a function called mandelbrot that takes a number n and prints out the Mandelbrot Set using ascii characters in an n x n matrix.

Stretch: tic-tac-toe

Write a tic-tac-toe game. Firstly, it should print out an empty grid, then wait for input. Players take turns entering coordinates in the form (x, y). The game adds a O or an X in the right square, then prints out the grid again.

Make good use of functions to split up your code. For example, you could write a function print_grid which takes the grid state as an argument and prints it to the console.

Stretch: Write a single-player game where the computer plays against you. Are you better at Python than you are at tic-tac-toe? :)

Testing

In the shell, in the labs directory, execute python tests.py. If you've followed all the instructions and done well in the labs, all the tests should pass. If you get test failures, the output will show you where you've gone wrong.

Testing is an important part of any software development process. "Testing" code using __main__() methods is brittle, because you need to execute them manually - meaning you might forget and check in buggy code.

In the next labs, we'll ask you to write your own tests before you even start writing code. This helps you think about the problem, and is a really great professional practice.

Finally

If you've been working in pairs, you'll both want a copy of the code. The other person should also take a fork of the codeabase and should accept a pull request for the changes, so that everyone has working labs.

Clone this wiki locally