python循环

loop

for in

#!/usr/bin/python3
 
sites = ["Baidu", "Google","Runoob","Taobao"]
for site in sites:
    if site == "Runoob":
        print("菜鸟教程!")
        break
    print("循环数据 " + site)
else:
    print("没有循环数据!")
print("完成循环!")

range() function

>>>for i in range(5):
...     print(i)
...
0
1
2
3
4

>>>for i in range(5,9) :
    print(i)
 
    
5
6
7
8
>>>

>>>for i in range(0, 10, 3) :
    print(i)
 
    
0
3
6
9
>>>

>>>for i in range(-10, -100, -30) :
    print(i)
 
    
-10
-40
-70
>>>

组合循环

>>>a = ['Google', 'Baidu', 'Runoob', 'Taobao', 'QQ']
>>> for i in range(len(a)):
...     print(i, a[i])
... 
0 Google
1 Baidu
2 Runoob
3 Taobao
4 QQ
>>>

List Comprehension

List comprehensions are one of Python's most beloved and unique features. The easiest way to understand them is probably to just look at a few examples:

squares = [n**2 for n in range(10)]
squares
# [0, 1, 4, 9, 16, 25, 36, 49, 64, 81]

Here's how we would do the same thing without a list comprehension:

squares = []
for n in range(10):
    squares.append(n**2)
squares

We can also add an if condition:

short_planets = [planet for planet in planets if len(planet) < 6]
short_planets
['Venus', 'Earth', 'Mars']