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HomeBackend DevelopmentPython TutorialPython 流程控制实例代码

首先,介绍if-else条件语句。if语句是用来根据表达式的真假来有选择的执行特定的程序块,控制程序的流程。用法同java等语言。对于else if,有一个elif的简写方式。
例如:

复制代码 代码如下:

if x > 3:
print("greater")
elif x == 3:
print("eq")
else:
print("small")

接下来介绍while语句。while语句的作用是在条件表达式为真时,重复执行特定的程序块。
首先看一段示例程序,然后在给予说明:
复制代码 代码如下:

x = int(input("enter a integer:"))
while x != -1:
print(x)
x = int(input("next number:"))
else:
print("end")
print('over')

在这段代码中,只要x的值不等于-1,就会重复的执行。相对于c/c++/java来讲,比较特殊的是那个else语句。在这里,else是一个可选的语句。当条件表达式为假,跳出while循环后,会执行else语句下的程序块。
最后,看一下for循环。for..in是Python中的另外一种循环语句。主要目的是为了迭代访问对象序列。使用方法如下:
复制代码 代码如下:

for x in range(1,5):
print(x)
print('over')

对于循环语句,需要有跳出当前循环和跳出循环的方法,在Python中,使用continue和break语句。对于这两个语法的使用,同c/c++/java,所以就不多复述了。
使用上述这三种方法,就可以完成Python中的所有的流程控制工作了!
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