条件语句：
#以缩进来区分表示同一范围。
1 # coding=utf8 2 # 例1：if 基本用法 3 4 flag = False 5 name = 'luren' 6 if name == 'python': # 判断变量否为'python' 7 flag = True # 条件成立时设置标志为真 8 print 'welcome boss' # 并输出欢迎信息 9 else: 10 print name # 条件不成立时输出变量名称
多重判断：
1 # coding=utf8 2 # 例2：elif用法 3 4 num = 5 5 if num == 3: # 判断num的值 6 print 'boss' 7 elif num == 2: 8 print 'user' 9 elif num == 1: 10 print 'worker' 11 elif num < 0: # 值小于零时输出 12 print 'error' 13 else: 14 print 'roadman' # 条件均不成立时输出
python 并不支持 switch 语句
1 # coding=utf8 2 # 例3：if语句多个条件 3 4 num = 9 5 if num >= 0 and num <= 10: # 判断值是否在0~10之间 6 print 'hello' 7 >>> hello # 输出结果 8 9 num = 10 10 if num < 0 or num > 10: # 判断值是否在小于0或大于10 11 print 'hello' 12 else: 13 print 'undefine' 14 >>> undefine # 输出结果 15 16 num = 8 17 # 判断值是否在0~5或者10~15之间 18 if (num >= 0 and num <= 5) or (num >= 10 and num <= 15): 19 print 'hello' 20 else: 21 print 'undefine' 22 >>> undefine # 输出结果
同一行，与IDL类似
1 #!/usr/bin/python 2 3 var = 100 4 5 if ( var == 100 ) : print "Value of expression is 100" 6 7 print "Good bye!"
循环语句：
while
1 #!/usr/bin/python 2 3 count = 0 4 while (count < 9): 5 print 'The count is:', count 6 count = count + 1 7 8 print "Good bye!"
while... else
1 #!/usr/bin/python 2 3 count = 0 4 while (count < 9): 5 print 'The count is:', count 6 count = count + 1 7 8 print "Good bye!"
1 #!/usr/bin/python 2 3 flag = 1 4 5 while (flag): print 'Given flag is really true!' 6 7 print "Good bye!"
while循环嵌套
1 #coding=utf-8 2 #!/usr/bin/python 3 4 i = 2 5 while(i < 100): 6 j = 2 7 while(j <= (i/j)): 8 if not(i%j): break 9 j = j + 1 10 if (j > i/j) : print i, " 是素数" 11 i = i + 1 12 13 print "Good bye!"
for
遍历任何序列的项目，列表或字符串
for i in sequence
statements(s)
1 #!/usr/bin/python 2 3 for letter in 'Python': # First Example 4 print 'Current Letter :', letter 5 6 fruits = ['banana', 'apple', 'mango'] 7 for fruit in fruits: # Second Example 8 print 'Current fruit :', fruit 9 10 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!
索引
1 #!/usr/bin/python 2 3 fruits = ['banana', 'apple', 'mango'] 4 for index in range(len(fruits)): 5 print 'Current fruit :', fruits[index] 6 7 print "Good bye!"
内置函数 len() 和 range(),函数 len() 返回列表的长度，即元素的个数。 range返回一个序列的数。
for.... else...（for循环嵌套）
1 #!/usr/bin/python 2 3 for num in range(10,20): #to iterate between 10 to 20 4 for i in range(2,num): #to iterate on the factors of the number 5 if num%i == 0: #to determine the first factor 6 j=num/i #to calculate the second factor 7 print '%d equals %d * %d' % (num,i,j) 8 break #to move to the next number, the #first FOR 9 else: # else part of the loop 10 print num, 'is a prime number'
break跳出整个循环 continue跳出本次循环 pass空语句，是为了保持程序结构的完整性。
1 #!/usr/bin/python 2 3 for letter in 'Python': 4 if letter == 'h': 5 pass 6 print 'This is pass block' 7 print 'Current Letter :', letter 8 9 print "Good bye!"