Python Advanced list processing

ADVANCED LIST PROCESSING

List Comprehension

List comprehension is an elegant and concise way to create new list from an existing list in Python.

List comprehension consists of an expression followed by for statement inside square brackets.

Here is an example to make a list with each item being increasing power of 2.

pow2 = [2 ** x for x in range(10)]

#  Output: [1, 2, 4, 8, 16, 32, 64, 128, 256, 512] print(pow2)

This code is equivalent to

pow2 = []

for x in range(10):

pow2.append(2 ** x)

A list comprehension can optionally contain more for or if statements. An optional if statement can filter out items for the new list.

Here are some examples.

>>>        pow2 = [2 ** x for x in range(10) if x > 5]

>>>        pow2

[64, 128, 256, 512]

>>>        odd = [x for x in range(20) if x % 2 == 1]

>>>        odd

[1, 3, 5, 7, 9, 11, 13, 15, 17, 19]

[x+y for x in ['Python ','C '] for y in ['Language','Programming']] ['Python Language', 'Python Programming', 'C Language', 'C Programming']