What does python library mean?

1. Python library (library)

The concept of a library is a collection of related functional modules. This is also one of the major features of Python, that is, it has a powerful standard library, third-party libraries and custom modules.

2. The python module is:

python module: Containing and organized code snippets are modules.

The expression is: the written code is saved as a file. This file is a module. sample.py where the file name smaple is the module name.

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The python package is:

The package is a hierarchical file directory structure, which defines n A python application execution environment composed of modules or n sub-packages. In layman's terms: a package is a directory containing an __init__.py file. This directory must have this __init__.py file and other modules or sub-packages.

FAQ:

Introduce a module under a specific path

Use sys.path.append(yourmodulepath)

Add a path to python Under the system path, avoid specifying the path through code every time

Use the system environment variable export PYTHONPATH=$PYTHONPATH:yourmodulepath,

Directly link this path to something like /Library/Python/2.7/site -

Good suggestions in the packages directory:

Always use if __name__ == '__main__' to ensure that the written package can be imported and run independently for testing.

Multiple imports will not execute the module multiple times, but only once. You can use reload to force the module to run, but it is not recommended.

The common package structure is as follows:

package_a├── __init__.py├── module_a1.py└── module_a2.pypackage_b├── __init__.py├── module_b1.py└ ── module_b2.py

main.py

If main.py wants to reference module modulea1 in packagea, you can use:

from package_a import module_a1

import package_a.module_a1

If modulea1 in packagea needs to reference packageb, then by default, python cannot find packageb. We can use sys.path.append('../'), add this sentence to __init__.py in packagea, and then add * import __init_ to all modules in the package.

Relationship diagram:

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