Double Iteration in List Comprehension

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Suppose you have a text full of sentences and you want an array of words.

# Without list comprehension
list_of_words = []
for sentence in text:
    for word in sentence:
       list_of_words.append(word)
return list_of_words

I like to think of list comprehension as stretching code horizontally.

Try breaking it up into:

# List Comprehension 
[word for sentence in text for word in sentence]

Example:

>>> text = (("Hi", "Steve!"), ("What's", "up?"))
>>> [word for sentence in text for word in sentence]
['Hi', 'Steve!', "What's", 'up?']

This also works for generators

>>> text = (("Hi", "Steve!"), ("What's", "up?"))
>>> gen = (word for sentence in text for word in sentence)
>>> for word in gen: print(word)
Hi
Steve!
What's
up?

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