Now we know enough about Python for creating a program that is actually useful. Awesome!
In this tutorial we'll write a program that reads questions and answers in a text file and asks them. For example, this file would make the program ask what "text displaying function" and "text asking function" are:
text displaying function = print
text asking function = input
Save this example file to questions.txt, we'll need it later.
This might seem useless to you right now, but a program like this can actually be really useful for learning different kinds of things. I originally wrote a program like this to study words of a foreign language, but then I realized that I could study pretty much anything with it.
But there are many things the program needs to do and writing it seems really difficult and complicated! How the heck can we do this?
Our program will need to do several different things:
- Read the questions from a file.
- Ask the questions.
- Print statistics about how many questions were answered correctly and how many wrong.
Now everything seems much easier. We know how to do each of these steps
one by one, but doing it all at once would be difficult. In situations
like this it's important to define functions.
We are going to write a read_questions function, an ask_questions
function and a stats function.
Let's start with the function that reads the question file:
def read_questions(filename):
answers = {}
with open(filename, 'r') as f:
for line in f:
line = line.strip()
if line != '':
question, answer = line.split('=')
answers[question.strip()] = answer.strip()
return answersAt this point it's best to try out the function to see how it works. You
need to create a questions.txt file like the one in the beginning of
this tutorial if you didn't create it already.
TODO: Instructions for using the -i switch.
>>> read_questions('questions.txt')
{'text displaying function': 'print', 'text asking function': 'input'}
>>>If your function doesn't work correctly it doesn't matter, and fixing the problem is easy because the function is so short. This is one of the reasons why we write functions.
Next we'll write the rest of the functions the same way, first writing and then testing and fixing. Here are my versions of them:
def ask_questions(answers):
correct = []
wrong = []
for question, answer in answers.items():
if input(question + ' = ').strip() == answer:
print("Correct!")
correct.append(question)
else:
print("Wrong! The correct answer is %s." % answer)
wrong.append(question)
return (correct, wrong)
def stats(correct, wrong, answers):
print("\n**** STATS ****\n")
print("You answered", len(correct), "questions correctly and",
len(wrong), "questions wrong.")
if wrong:
print("These would have been the correct answers:")
for question in wrong:
print(' ', question, '=', answers[question])Note that these functions have some empty lines in them and there are two empty lines between the functions. This makes the code a bit longer, but it's a lot easier to read this way.
Let's try out the functions.
>>> answers = read_questions('questions.txt')
>>> correct, wrong = ask_questions(answers)
text displaying function = print
Correct!
text asking function = elif
Wrong! The correct answer is input.
>>> correct
['text displaying function']
>>> wrong
['text asking function']
>>> stats(correct, wrong, answers)
**** STATS ****
You answered 1 questions right and 1 questions wrong.
These would have been the correct answers:
text asking function = input
>>>Everything is working! Now we just need something that runs everything
because we don't want to type this out on the >>> prompt every time.
You might have noticed that the stats function printed 1 questions
instead of 1 question, and it looks a bit weird. You can modify the
print_stats function to fix this if you want to.
The last function in a program like this is usually called main and it
runs the program using other functions. Our main function consists of
mostly the same pieces of code that we just tried out on the >>>
prompt.
def main():
filename = input("Name of the question file: ")
answers = read_questions(filename)
correct, wrong = ask_questions(answers)
stats(correct, wrong, answers)The last thing we need to add is these two lines:
if __name__ == '__main__':
main()The __name__ variable is set differently depending on how we run the
file, and it's '__main__' when we run the file directly instead of
importing. So if we run the file normally it asks us the words, and if
we import it instead we can still run the functions one by one. If you
want to know more about __name__ just make a file that prints it and
run it in different ways.
Now the whole program looks like this:
def read_questions(filename):
answers = {}
with open(filename, 'r') as f:
for line in f:
line = line.strip()
if line != '':
question, answer = line.split('=')
answers[question.strip()] = answer.strip()
return answers
def ask_questions(answers):
correct = []
wrong = []
for question, answer in answers.items():
if input('%s = ' % question).strip() == answer:
print("Correct!")
correct.append(question)
else:
print("Wrong! The correct answer is %s." % answer)
wrong.append(question)
return (correct, wrong)
def stats(correct, wrong, answers):
print("\n**** STATS ****\n")
print("You answered", len(correct), "questions correctly and",
len(wrong), "questions wrong.")
if wrong:
print("These would have been the correct answers:")
for question in wrong:
print(' ', question, '=', answers[question])
def main():
filename = input("Name of the question file: ")
answers = read_questions(filename)
correct, wrong = ask_questions(answers)
stats(correct, wrong, answers)
if __name__ == '__main__':
main()This is just the beginning. Now you can take your word asking program and make your own version of it that suits your needs. Then you can share it with your friends so they will find it useful as well.
- Make multiple functions when your program needs to do multiple things. Each function should do one thing.
- Try out the functions on the
>>>prompt when you want to check if they work correctly. __name__is'__main__'when the program is supposed to run, and something else when it's imported.
If you have trouble with this tutorial please tell me about it and I'll make this tutorial better. If you like this tutorial, please give it a star.
You may use this tutorial freely at your own risk. See LICENSE.