Python教程-循环语句

最新推荐文章于 2025-08-08 11:09:55 发布

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最新推荐文章于 2025-08-08 11:09:55 发布

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文章标签： python

原文链接：https://my.oschina.net/CeShiXiaoSongShu/blog/787990

本文详细介绍了Python中的循环结构，包括while循环和for循环的使用方法，并通过实例演示了如何运用这些循环来解决实际问题，例如查找素数和遍历字符串等。

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while

1、http://www.yiibai.com/python/python_loops.html

2、http://www.yiibai.com/python/python_while_loop.html

3、http://www.cnblogs.com/way_testlife/archive/2010/06/14/1758276.html

4、http://www.runoob.com/python/python-while-loop.html

while expression:
   statement(s)

#!/usr/bin/python

count = 0
while (count < 9):
   print 'The count is:', count
   count = count + 1

print "Good bye!"

The count is: 0
The count is: 1
The count is: 2
The count is: 3
The count is: 4
The count is: 5
The count is: 6
The count is: 7
The count is: 8
Good bye!

The Infinite Loop:

#!/usr/bin/python

var = 1
while var == 1 :  # This constructs an infinite loop
   num = raw_input("Enter a number  :")
   print "You entered: ", num

print "Good bye!"

Enter a number  :20
You entered:  20
Enter a number  :29
You entered:  29
Enter a number  :3
You entered:  3
Enter a number between :Traceback (most recent call last):
  File "test.py", line 5, in <module>
    num = raw_input("Enter a number :")
KeyboardInterrupt

The else Statement Used with Loops

#!/usr/bin/python

count = 0
while count < 5:
   print count, " is  less than 5"
   count = count + 1
else:
   print count, " is not less than 5"

0 is less than 5
1 is less than 5
2 is less than 5
3 is less than 5
4 is less than 5
5 is not less than 5

Single Statement Suites:

#!/usr/bin/python

flag = 1

while (flag): print 'Given flag is really true!'

print "Good bye!"

for

1、http://www.yiibai.com/python/python_for_loop.html

for iterating_var in sequence:
   statements(s)

#!/usr/bin/python

for letter in 'Python':     # First Example
   print 'Current Letter :', letter

fruits = ['banana', 'apple',  'mango']
for fruit in fruits:        # Second Example
   print 'Current fruit :', fruit

print "Good bye!"

Current Letter : P
Current Letter : y
Current Letter : t
Current Letter : h
Current Letter : o
Current Letter : n
Current fruit : banana
Current fruit : apple
Current fruit : mango
Good bye!

内嵌循环

1、http://www.yiibai.com/python/python_nested_loops.html

for iterating_var in sequence:
   for iterating_var in sequence:
      statements(s)
   statements(s)

while expression:
   while expression:
      statement(s)
   statement(s)

#!/usr/bin/python

i = 2
while(i < 100):
   j = 2
   while(j <= (i/j)):
      if not(i%j): break
      j = j + 1
   if (j > i/j) : print i, " is prime"
   i = i + 1

print "Good bye!"

2 is prime
3 is prime
5 is prime
7 is prime
11 is prime
13 is prime
17 is prime
19 is prime
23 is prime
29 is prime
31 is prime
37 is prime
41 is prime
43 is prime
47 is prime
53 is prime
59 is prime
61 is prime
67 is prime
71 is prime
73 is prime
79 is prime
83 is prime
89 is prime
97 is prime
Good bye!

循环控制语句：

break

#!/usr/bin/python

for letter in 'Python':     # First Example
   if letter == 'h':
      break
   print 'Current Letter :', letter
  
var = 10                    # Second Example
while var > 0:              
   print 'Current variable value :', var
   var = var -1
   if var == 5:
      break

print "Good bye!"

Current Letter : P
Current Letter : y
Current Letter : t
Current Letter : o
Current Letter : n
Current variable value : 9
Current variable value : 8
Current variable value : 7
Current variable value : 6
Current variable value : 4
Current variable value : 3
Current variable value : 2
Current variable value : 1
Current variable value : 0
Good bye!

pass

#!/usr/bin/python

for letter in 'Python': 
   if letter == 'h':
      pass
      print 'This is pass block'
   print 'Current Letter :', letter

print "Good bye!"

Current Letter : P
Current Letter : y
Current Letter : t
This is pass block
Current Letter : h
Current Letter : o
Current Letter : n
Good bye!

continue

#!/usr/bin/python

for letter in 'Python':     # First Example
   if letter == 'h':
      continue
   print 'Current Letter :', letter

var = 10                    # Second Example
while var > 0:              
   var = var -1
   if var == 5:
      continue
   print 'Current variable value :', var
print "Good bye!"

Current Letter : P
Current Letter : y
Current Letter : t
Current Letter : o
Current Letter : n
Current variable value : 9
Current variable value : 8
Current variable value : 7
Current variable value : 6
Current variable value : 4
Current variable value : 3
Current variable value : 2
Current variable value : 1
Current variable value : 0
Good bye!

转载于:https://my.oschina.net/CeShiXiaoSongShu/blog/787990