python for循环及常用函数

python for循环

格式:

for iterating_var in sequence:

   statements(s)

########################################

可多层嵌套

for iterating_var in sequence:

    for iterating_var in sequence:

        statements(s)

        for iterating_var in sequence:

            ...

    statements(s)

常用函数

enumerate()

对于字典,返回key的下标和key本身的值

info = {'name':'lijiang', 'age':0, 'a':100}

print(info)

for key, valuel in enumerate(info):

    print(key, valuel)

执行

C:\Python27\python.exe D:/Python/type-of-data.py

{'a': 100, 'age': 0, 'name': 'lijiang'}

(0, 'a')

(1, 'age')

(2, 'name')

Process finished with exit code 0

############################################################################

对于更序列(列表、元组或字符串),返回下标及下标对应的值,以字符串为例:

name = 'lijiang'

for key, valuel in enumerate(name):

    print(key, valuel)

执行

C:\Python27\python.exe D:/Python/type-of-data.py

(0, 'l')

(1, 'i')

(2, 'j')

(3, 'i')

(4, 'a')

(5, 'n')

(6, 'g')

Process finished with exit code 0

iteritems()

info = {'name':'lijiang', 'age':0, 'a':100}

for key, valuel in info.iteritems():

    print(key, valuel)

执行:

C:\Python27\python.exe D:/Python/type-of-data.py

('a', 100)

('age', 0)

('name', 'lijiang')

Process finished with exit code 0

range() 和 xrange()

print(range(10))

print(type(range(10)))

print(xrange(10))

print(type(xrange(10)))

执行

C:\Python27\python.exe D:/Python/type-of-data.py

[0, 1, 2, 3, 4, 5, 6, 7, 8, 9]

<type 'list'>

xrange(10)

<type 'xrange'>

Process finished with exit code 0