Python 中的条件编译 [英] Conditional compilation in Python

问题描述

如何在 Python 中进行条件编译?

How to do conditional compilation in Python ?

是否使用 DEF ?

推荐答案

Python 与 C 或 C++ 甚至 Java 的编译意义不同，python 文件是动态"编译的，您可以将其视为类似于 Basic 或 Perl 等解释型语言.₁

Python isn't compiled in the same sense as C or C++ or even Java, python files are compiled "on the fly", you can think of it as being similar to a interpreted language like Basic or Perl.₁

您可以通过仅使用 if 语句来执行与条件编译等效的操作.例如:

You can do something equivalent to conditional compile by just using an if statement. For example:

if FLAG:
    def f():
        print "Flag is set"
else:
    def f():
        print "Flag is not set"

您可以对创建类、变量设置和几乎所有内容执行相同操作.

You can do the same for the creation classes, setting of variables and pretty much everything.

模仿 IFDEF 的最接近方法是使用 hasattr 函数.例如:

The closest way to mimic IFDEF would be to use the hasattr function. E.g.:

if hasattr(aModule, 'FLAG'):
    # do stuff if FLAG is defined in the current module.

您也可以使用 try/except 子句来捕获名称错误，但惯用的方法是在脚本顶部将变量设置为 None.

You could also use a try/except clause to catch name errors, but the idiomatic way would be to set a variable to None at the top of your script.

1. Python 代码被字节编译成 Java 等中间形式，但通常没有单独的编译步骤.以 .py 结尾的原始"源文件是可执行的.

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