python入门--else-for-while语句篇

python if 语句
格式： (必须注意 if 、elif 、 else后面均带冒号，并且语句块必须缩进)
      if 表达式 :
           语句块
      elif 表达式:
           语句块
      else:
           语句块
 
eg:
   tmp = int(raw_input("please input a integer"))
   if tmp < 10:
       print tmp ,' < 10'
   elif tmp >=10 and tmp < 20:
       print '10 <= ' ,tmp , ' < 20'
   else:
       print '20 <= ' , tmp
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python for 语句
格式1：
str = ['Monday', 'Tuesday', 'Thirsday', 'Wendesday', 'Friday']
for x in str:
      print x, len(x)

格式2：
str = ['Monday', 'Tuesday', 'Thirsday', 'Wendesday', 'Friday']
for x in str[:]:
     print x, len(x)

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range 产生等差级数列
>>>range(10)
[0,1,2,3,4,5,6,7,8,9]

结合range、len遍历链表
for i in (range(len(str))):
      print str[i], len(str[i])

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python while 语句

while 表达式:
      语句块

eg:
   tmp = 10
   while tmp > 0:
          print tmp
          tmp = tmp - 1
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