如何阻止 python 查找 .py 文件

Question

我有一个资源很少（嵌入式）的系统。因此，我只为我的程序安装了 python .pyo 文件（=字节编译和优化）。现在，当这样的程序运行时，python 会不断寻找 .py 文件（可能是为了查看 .pyo 是否需要更新）。有趣的是，它做了很多事情：5 分钟内 25000 次 stat64() 调用（和 8304 次 getcwd 调用（））！

getcwd("/tmp", 1026)                = 9
getcwd("/tmp", 1026)                = 9
stat64("MyProgram.py", 0xbeb94b0c) = -1 ENOENT (No such file or directory)
stat64("/usr/local/lib/python2.5/MyProgram.py", 0xbeb94b0c) = -1 ENOENT (No such file or directory)
stat64("/usr/local/lib/python25.zip/MyProgram.py", 0xbeb94b0c) = -1 ENOENT (No such file or directory)
stat64("/usr/local/lib/python2.5/MyProgram.py", 0xbeb94b0c) = -1 ENOENT (No such file or directory)
stat64("/usr/local/lib/python2.5/plat-linux2/MyProgram.py", 0xbeb94b0c) = -1 ENOENT (No such file or directory)
stat64("/usr/local/lib/python2.5/lib-tk/MyProgram.py", 0xbeb94b0c) = -1 ENOENT (No such file or directory)
stat64("/usr/local/lib/python2.5/lib-dynload/MyProgram.py", 0xbeb94b0c) = -1 ENOENT (No such file or directory)
stat64("MyProgram.py", 0xbeb94cc8) = -1 ENOENT (No such file or directory)
getcwd("/tmp", 1026)                = 9
stat64("MyProgram.py", 0xbeb94bc4) = -1 ENOENT (No such file or directory)

如何防止python这样做？

Answer 1

您可以尝试__builtins__.__import__用自己的代码替换该函数（由 import 语句调用）。您可以使用该imp.load_module函数加载 py/pyc/pyo 文件。

这是它的一个非常简单的版本：

import sys
import imp

real_import = __builtins__.__import__

def pyc_only_import(name, globals = globals(), locals = locals(), fromlist = [], level = 0):
    pycname = name + ".pyc"
    modfile = open(pycname)
    return imp.load_module(name, modfile, pycname, (".pyc", "rb", 2))

__builtins__.__import__ = pyc_only_import

import hello

这远未完全实现__import__，但如果当前工作目录中有 hello.pyc 文件，它就可以工作。