.pyc文件

• 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.
• When a script is run by giving its name on the command line, the bytecode for the script is never written to a ‘.pyc’ or ‘.pyo’ file. Thus, the startup time of a script may be reduced by moving most of its code to a module and having a small bootstrap script that imports that module. It is also possible to name a ‘.pyc’ or ‘.pyo’file directly on the command line.

　　　在你 import 别的 py 文件时，那个 py 文件会被存一份 pyc 加速下次装载。而主文件因为只需要装载一次就没有存pyc，你可以写两个 a.py 和 b.py，一个 import 另一个试试看。  

　　　作者：李璜
　　　链接：https://www.zhihu.com/question/30296617/answer/47512467
　　　来源：知乎

 

　　　.pcy是预编译后的字节码（Not机器码），当import其他py文件时，那个py文件会在自己目录产生__pycache__/xx.pyc文件，相当于先编译了要导入的py文件。