[Python Cookbook] Iteration over a List in Python

For Loop

ls = [1, 2, 3, 4]
for i in ls:
    print (i)

 

Enumerate Method

ls = [1, 2, 3, 4]
for i, j in enumerate(ls):
    print(i, j)

Out:

　　0 1

　　1 2

　　2 3

　　3 4

List Comprehension

Syntax:

new_list = [expression(i) for i in old_list if filter(i)]

It's equivalent to

new_list = []
for i in old_list:
    if filter(i):
        new_list.append(expressions(i))