4.1 `if` 语句 `if` Statements

Perhaps the most well-known statement type is the if statement. For example:

也许最有名的是 if 语句。例如：

>>> x = int(raw_input("Please enter an integer: "))
>>> if x < 0:
...      x = 0
...      print 'Negative changed to zero'
... elif x == 0:
...      print 'Zero'
... elif x == 1:
...      print 'Single'
... else:
...      print 'More'
...

There can be zero or more elif parts, and the else part is optional. The keyword `elif' is short for `else if', and is useful to avoid excessive indentation. An if ... elif ... elif ... sequence is a substitute for the switch or case statements found in other languages.

可能会有 0 或很多个 elif 部分，else 是可选的。关键字“elif ” 是“ else if ”的缩写，这个可以有效避免过深的缩进。if ... elif ... elif ... 序列用于替代其它语言中的 switch 或 case 语句。

4.1 if 语句 if Statements

4.1 `if` 语句 `if` Statements