I decided to start my Python challenge with a bunch of warmup exercises simply to get a feeling for the syntax and for how to work with that language. This exercises include:

  • hello world and running python
  • getting the user’s input
  • handling command line arguments
  • working with functions
  • writing test cases

How to execute a simple ‘hello world’?

After installing python 3, I took the classic hello world example

print("hello world")

…and executed it like this:

python3 hello.py

How to get the user’s input?

print("Demo of user input")
print("")
response = input("Please enter your name: ")
print ("Hello, ", response)


The user’s input can be caught by the input function followed by a message.

How to handle command line arguments?

import sys
print("Demo of CLI handling")
print("")
print("Number of CLI args: ", len(sys.argv))
print("CLI args: ", str(sys.argv))


In order to handle command line arguments, the sys module needs to be imported.
The arguments themselves are stored in the argv array

Implementing a simple function

def sum(a, b):
  return a + b

print("calling sum...")
print(sum(5,5))


A function starts with the keyword def followed by the name and parameters if suitable.
The function’s body needs to be indented.

Writing a test case

Usually, Python is not strictly object-oriented. Test cases however are implemented as classes.
The following is a test class that contains a test case for the sum function above:

import unittest
from sum_function import sum

class SumTestCase(unittest.TestCase):
  def test_sum(self):
    self.assertTrue(sum(5,5)==10)

if __name__ == '__main__':
  unittest.main()

A couple of things are to consider here:

  • Note that the class SumTestCase inherits from the class TestCase, that is imported from the module unittest.
  • The function under test (in this case sum) is imported
  • The function test_sum performs the actual test by calling self.assertTrue
  • ’ name’ is a built-in variable that checks if the script is executed directly or if it is imported by another module. If it is executed directly the main funtion of unittest will be called. In other words, the test case will be executed.

Further resources

My python challenge