Overview
List comprehension is an easy way of generating a list, that can be described mathematically.
Example 1
If we wanted to generate a list of the odd numbers from 1 to 100, we could create this with the following list comprehension.
oddlist = [i for i in range(100) if not i % 2 ==0]
This returns:
[1, 3, 5, 7, 9, 11, 13, 15, 17, 19, 21, 23, 25, 27, 29, 31, 33, 35, 37, 39, 41, 43, 45, 47, 49, 51, 53, 55, 57, 59, 61, 63, 65, 67, 69, 71, 73, 75, 77, 79, 81, 83, 85, 87, 89, 91, 93, 95, 97, 99]
Example 2
Here is another example, try to follow what it is doing.
examplelist = [x * 6 for x in range(5,20,2)]
Returns:
[30, 42, 54, 66, 78, 90, 102, 114]
Example Strings
If we have a string
S = "the boat is sinking"
We can use the split function to turn this sentence into a list of
words
S = s.split()
This returns:
['the', 'boat', 'is', 'sinking']
We can the operate on this list to generate more lists.
s = 'The boat is sinking' s = s.split() s = [[i.upper(), i.lower(), i + " end"] for i in s] print (s)
This returns:
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[['THE', 'the', 'The end'], ['BOAT', 'boat', 'boat end'], ['IS', 'is', 'is end'], ['SINKING', 'sinking', 'sinking end']]
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