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首页精彩阅读python中pyc和pyo的作用
python中pyc和pyo的作用
2017-03-17
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python中pyc和pyo的作用

pyc文件,是Python编译后的字节码(bytecode)文件。只要你运行了py文件,python编译器就会自动生成一个对应的pyc字节码文件。这个pyc字节码文件,经过python解释器,会生成机器码运行(这也是为什么pyc文件可以跨平台部署,类似于Java的跨平台,java中JVM运行的字节码文件)。下次调用直接调用pyc,而不调用py文件。直到你这个py文件有改变。python解释器会检查pyc文件中的生成时间,对比py文件的修改时间,如果py更新,那么就生成新的pyc。
    pyo文件,是python编译优化后的字节码文件。pyo文件在大小上,一般小于等于pyc文件。如果想得到某个py文件的pyo文件,可以这样:
python -O -m py_compile xxxx.py
    python文档是这样描述的:这个优化没有多大作用,只是移除了断言。原文如下:
    When the Python interpreter is invoked with the -O flag, optimized code is generated and stored in .pyo files. The optimizer currently doesn’t help much; it only removes assert statements. When -O is used, all bytecode is optimized; .pyc files are ignored and .py files are compiled to optimized bytecode.
    
    至于速度,运行几乎一样,加载pyc和pyo稍占优势。python文档是这样说的:   
    A program doesn’t run any faster when it is read from a .pyc or .pyo file than when it is read from a .py file; the only thing that’s faster about .pyc or .pyo files is the speed with which they are loaded.

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