如果import语句仅包含文件名，python如何找到模块文件？

Question

Everywhere I see Python code importing modules using import sys or import mymodule

How does the interpreter find the correct file if no directory or path is provided?

Answer 1

http://docs.python.org/3/tutorial/modules.html#the-module-search-path

6.1.2. The Module Search Path

When a module named spam is imported, the interpreter first searches for a built-in module with that name. If not found, it then searches for a file named spam.py in a list of directories given by the variable sys.path . sys.path is initialized from these locations:

• The directory containing the input script (or the current directory when no file is specified).
• PYTHONPATH (a list of directory names, with the same syntax as the shell variable PATH ).
• The installation-dependent default.

Note: On file systems which support symlinks, the directory containing the input script is calculated after the symlink is followed. In other words the directory containing the symlink is not added to the module search path.

After initialization, Python programs can modify sys.path . The directory containing the script being run is placed at the beginning of the search path, ahead of the standard library path. This means that scripts in that directory will be loaded instead of modules of the same name in the library directory. This is an error unless the replacement is intended. See section Standard Modules for more information.

For information on the "installation-specific default", see documentation on the site module .

Answer 2

Also, you can see what the current path is by using the sys module

import sys
print(sys.path)

Answer 3

它使用设置为环境变量的PYTHONPATH查找包（包含__init__.py文件的文件夹）和模块（或者，如果已经加载一次，则从sys.modules检索模块对象）。

Answer 4

Python has a path variable just like the one you have inside your terminal. Python looks for modules in folders inside that path, or in the folder where your program is located.