Python学习笔记：03语法

Python 语法

Python语法包括：

• 模块函数导入
• 赋值
• 判断循环语句

模块导入

import somemodule

somemodule.somefunc

from somemodule import somefunc

somefunc

import math
math.pow(2,3)

8.0

from math import pow
pow(2,3)

8.0

赋值

• 序列解包
• 链式赋值
• 增量赋值

x,y=1,2
x,y

(1, 2)

x,y=y,x
x,y

(2, 1)

x=y=3
x,y

(3, 3)

x+=1
x

4

判断语句

if 条件

条件包括：>,>=,<,<=,!=,<>,==,in,not,and,or

x=10
if x>5:
    print 'greater'
else:
    print 'less'

greater

x=10
assert x > 5

x=1
assert x > 1

---------------------------------------------------------------------------

AssertionError                            Traceback (most recent call last)

<ipython-input-13-693571434f5b> in <module>()
      1 x=1
----> 2 assert x > 1

AssertionError:

while循环

i=1
sum=0
while i<100:
    sum+=i
    i+=1
sum

4950

for循环

sum=0
for i in range(1,100):
    sum+=i
sum

4950

循环立遍字典元素

d={'x':1,'y':2,'z':3}
for key, value in d.items():
    print key,value

y 2
x 1
z 3

a=['x','y','z']
b=[1,2,3]
zip(a,b)

[('x', 1), ('y', 2), ('z', 3)]

for name,value in zip(a,b):
    print name,value

x 1
y 2
z 3

strings=['hello','hi','apple']
for index, string in enumerate(strings):
    if 'h' in string:
        strings[index]='replaced'
strings

['replaced', 'replaced', 'apple']

break,else语句

from math import sqrt
for n in range(99,1,-1):
    root=sqrt(n)
    if root==int(root):
        print n
        break
else:
    print 'did not find it'

81