Python基础概念2

 1.bool变量及运算

print 1 + 1 == 2
print 1 + 1 != 2

print 1 + 1 == 2 and 1 + 1 == 3
print 1 + 1 == 2 or 1 + 1 == 3

print not 1 + 1 == 2

print 1 in [1, 2, 3]

 

 输出: 

True
False
False
True
False
True

 

 2.if

light = "red"
if light == "red":
    print "Stop!"
elif light == "green":
    print "Go!"
elif light == "yellow":
    print "Slow down!"

 

3.while

a = 100

while a<100:

         a = a +1

print a

 

4. for in

contact = {"Li Lei" : "1303030", "HanMeimei" : "1450303"}
for i in contact:
    print i, contact[i]

输出： 

"Li Lei" : "1303030"

"HanMeimei" : "1450303"

5.break continue

意思与其他大部分语言相同

 

6.自定义函数

def addNum(num):
     a = 0
     for i in num:
          a = a + i
     return a

num = [ 1 ,3 ,4 ,5 , 9]

print addNum(num)

 

7.函数作用域

与C++很像

 

x =  0
y = 0
def changex():
     global x   //global 可以在函数里面使用函数外面的变量
     x = 10
     y = 10
     print x
     print y
changex()
print x
print y

 

 

8.import

import math  //导入包

print math.pi

print dir(math)  //dir可以查看包的所有方法