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Python Python Collections (2016, retired 2019) Lists Disemvowel

Mark Miller
Mark Miller
45,831 Points

How does python know where the end of a for-loop code block is? There's no indication of when execution should restart.

I can't use "continue" or "break" because the code block should execute for each item, and then break when no further items are available. The code block in a for loop (in python) has no curly braces nor an "end" keyword indicating the point where the block terminates. All other languages have the code block wrapped in some way to move execution back to the top for each item.

disemvowel.py
def disemvowel(word):
    vowels = ['a', 'e', 'i', 'o', 'u', 'A', 'E', 'I', 'O', 'U']
    container = list(word)
    for letter in vowels:
        try:
            container.remove(letter)
            except ValueError:
                pass

    new_word = ''.join(container)    
    return new_word

1 Answer

You have to use indentation to represent something is for something else:

for x in range(10):
    # all code indented are in the for loop
    print("This is *in* the for loop!")
    print("So as this!")
print("This is OUTSIDE of the for loop because it isn't indented.")

This is just a simple example, but it can get more complicated:

for x in range(10):
    # This is in the loop
    print("We are currently on the number {}!".format(x))

    if x == 5:
        # This is in the if statenent which is in the loop
        print("Cool! 5!")

    if x % 2 == 0:
        # This is in a different if statement but still in the loop
        print("Alright! {} is an even number!".format(x))

    # This is in the for loop but not in a if statement
    print("Next number coming up... {}!".format(x+1))

# This code isn't in any kind of block
print("Finished!")

This is why Python is so picky about indentation. If you forgot to indent like this:

for x in range(5):
    if x == 5:
    break

Python will cause an Syntax Error because it thought you put nothing in the if statement and there has to be something. Python also will think that the break command is part of the loop, but we really don't mean that. Keep in mind that you have to be very careful indenting when you are a beginner! You get used to it when you get more advanced :)

I hope this helps. ~Alex

Mark Miller
Mark Miller
45,831 Points

Thanks. I did not know indentation has meaning.

No problem :)