python 笔记4 流程控制

1.if  else  流程控制

/*1.py*/
#!/usr/bin/python
if 1<2: /*前面有冒号*/
    print "ok" /*统一空四个空格*/
    print "ok" /*统一空四个空格,在同一个运算条件中*/
/*相当于C 语言中的{ }将两行，扩起来*/
/*************************************************
打印出两个ok
****************************************************/
执行： python 1.py
ok
ok
***************************************************

/*2.py*/

#!/usr/bin/python
if True: /*以冒号结束 ,首字母大写  True    False*/
    print "ok" /*四个空格*/
print "false" /* 当条件不成立时执行，print "false"*/

/*Flase.py*/

#!/usr/bin/python
if False:
    print "ok"
print "false"

2。增加函数

#!/usr/bin/python
def fun():
    return 1
if fun():
    print "ok"
/********************/
python 1.py
ok

3.else

#!/usr/bin/python
def fun():
    return 1
if 0:
    print "ok"
else:            /*冒号*/
    print "bad"

4.elif的用法

#!/usr/bin/python
def fun():
    return 0
x=int(raw_input("please input:"))
if x>=90:
    print "A"
elif  x>=80:
    print "B"
elif   x>=70:
    print "C"
else :
    print "bad"

5逻辑关系.and  or not 相当于 and 就是&  

#!/usr/bin/python
x=int(raw_input("please input:"))
y=int(raw_input("please input:"))
if x>=90 and y>=90:
    print "A"
elif  x>=80:
    print "B"
elif   x>=70:
    print "C"
else :
    print "bad"

*************************
python 1.py
please input:90
please input:90
A

6.for循环

#!/usr/bin/python
for x in "abcd":
    print  x,"hello world"
**********************
python 1.py
a,hello world
b,hello world
c,hello world
d,hello world

7.range(10)

#!/usr/bin/python
for x in range(10):
    print x, "hello world"
*************************
python 1.py
0 hello world
1 hello world
2 hello world
3 hello world
4 hello world
5 hello world
6 hello world
7 hello world
8 hello world
9 hello world

8.range(1,11,2)  //第一个为初始值，第二个为结束值，第三个为步长

#!/usr/bin/python
for x in range(1,11,2):
    print x, "hello world"
python 1.py 
1 hello world
3 hello world
5 hello world
7 hello world
9 hello world

9.range(1,101)

#!/usr/bin/python
num=0
for x in range(1,101):
    num+=x
print num


************
5050

#!/usr/bin/python
num=0
for x in range(1,101):
    num+=x
print num


************
5050

10.for遍历列表中的值

#!/usr/bin/python
fruits=['bana','apple','man','str']
for x in range(len(fruits)):
    print 'Current fruit:',fruits[x]



***********************
python 1.py
Current fruit: bana
Current fruit: apple
Current fruit: man
Current fruit: str