Preface
During the execution of Python programs, some intermediate files will be generated, the most common of which is the pyc file. The pyc file is a binary bytecode file of Python. Understanding the role and generation mechanism of pyc files is of great significance to optimizing the running efficiency of Python programs, protecting source code, and cross-platform deployment. This article will explain the relevant knowledge of pyc files easily and easily through concise language, actual code and cases.
1. What is a pyc file
The pyc file is a Python binary file and is generated after compilation of the py file. A pyc file is a byte code (byte code), which is an intermediate form of execution by Python virtual machines. When a Python program is run, it is first compiled into bytecode, and then interpreted and executed by the Python virtual machine. The existence of pyc files can speed up the running of Python programs and it is cross-platform.
To give a simple example, suppose we have a Python file:
#
def greet(name):
return f"Hello, {name}!"When we run this file, Python will automatically generate files in the same directory. This file can be found in the pycache folder.
2. Generation and loading of pyc files
The pyc file is not necessarily generated, it is mainly generated in the following situations:
When called as a module: When a Python script is called as a module by other script files, a pyc file will be generated. For example, if we have a script file, import the file through import in another script file, and after running the file, a file will be generated in the path where the file is located.
import image
#
def generate_captcha():
# Logic for generating verification codes pass
#
image.generate_captcha()Generate through command line parameters: You can use command line parameters provided by Python to generate pyc files. For example, use the -m parameter:
python -m py_compile
Generate through code: Python provides the built-in py_compile module that can compile py files into pyc files.
import py_compile
py_compile.compile('')In addition, Python also provides the compileall module, which can recursively compile py files in the entire folder into pyc files.
import compileall
compileall.compile_dir('path/to/your/folder')When a Python program runs, it will first look for the pyc file in the hard disk. If found, it is loaded directly; if not found, it is compiled and generates a pyc file. Therefore, pyc files are actually a persistent way of saving PyCodeObject (bytecode object).
3. The role of pyc files
The existence of pyc files mainly has the following functions:
- Improve operational efficiency: Python is an interpreted language, and it needs to be explained and executed through the Python interpreter when running. The biggest problem with interpreted languages is that they run slower than compiled languages, because compiled languages will generate binary executable files, that is, machine instructions that do not cross-platform. The pyc file is a Python intermediate bytecode file, which can save the time and time of compilation and improve the running speed of the program to a certain extent.
- Prevent source code leakage: Because the source code can be directly seen in py files, if it is developing commercial software, it is impossible to leak the source code. After compiling it into pyc and then publishing it, it can prevent source code leakage to a certain extent. Although pyc files can be decompiled, the decompilation process is relatively complicated, and the compiled pyc files are different after different versions.
- Cross-platform deployment: pyc files are cross-platform bytecode executed by Python virtual machines. They are similar to Java or .NET virtual machines, which can be run across platforms.
4. The relationship between pyc files and Python versions
The contents of the pyc file are related to the Python version. The pyc files compiled by different versions are different. For example, the pyc files compiled with Python 2.5 cannot be executed in Python 2.4.
This is because Python's bytecode instruction set may vary in different versions, so the generated pyc files are also incompatible. In actual development, if you find that a pyc file cannot be executed in the current version of Python, you can try to delete the pyc file, then rerun the corresponding py file to generate a new pyc file.
5. pyc file and module import
In Python, a pyc file is generated only when the file is imported as a module. That is, the Python interpreter believes that only modules made by import need to be reused. The benefits of generating pyc files are obvious, and when we run the program multiple times, we don't need to reinterpret the module.
For example, suppose we have a module math_utils.py that defines some mathematical operations:
# math_utils.py
def add(a, b):
return a + b
def subtract(a, b):
return a - bImport and use this module in another script:
#
import math_utils
result_add = math_utils.add(5, 3)
result_subtract = math_utils.subtract(5, 3)
print(f"Addition: {result_add}")
print(f"Subtraction: {result_subtract}")When we first run it, the Python interpreter finds the math_utils.py file, compiles it into the math_utils.pyc file, and then executes it. When run again, the Python interpreter loads the math_utils.pyc file directly without recompiling the math_utils.py file.
6. Optimization of pyc file
In addition to ordinary pyc files, Python also provides optimized pyc files, i.e. pyo files. Use the -O parameter to compile the source program into a pyo file.
python -O -m py_compile
The pyo file is smaller than the pyc file and can also increase the loading speed. For embedded systems, it can compile the required modules into pyo files to reduce capacity.
# Sample codeimport py_compile
py_compile.compile('', optimize=2) # optimize=2 Indicates further removal of the document string7. pyc file and dynamic link library
In addition to pyc and pyo files, Python has another intermediate file, namely pyd files. The pyd file is a dynamic link library for Python, similar to the dll file in C/C++.
On Windows platforms, pyd files are generated when using certain extension modules, such as modules written in Cython. These files contain compiled binary code and can be called directly by Python.
8. Use cases of pyc file
The following is a specific case to demonstrate how to use pyc files.
Suppose we have a simple Python project with the following project structure:
my_project/
│
├──
├──
└──
Among them, and are two module files and are the main program file.
#
def func1():
print("Function 1 in module1")
#
def func2():
print("Function 2 in module2")
#
import module1
import module2
module1.func1()
module2.func2()Generate pyc file:
First, we need to generate the pyc file. You can use the compileall module to recursively compile py files in the entire project folder.
python -m compileall my_project/
After execution, a pycache folder will be generated under the my_project folder, which contains the and \ files.
Run the pyc file:
Then, we can run the file directly. Since and have been compiled into pyc files, the Python interpreter will load these pyc files directly without recompiling.
python my_project/
The output result is:
Function 1 in module1
Function 2 in module2
Delete py file:
To verify that the pyc file can exist independently and be executed, we can delete and file.
rm my_project/
rm my_project/
Then run the file again, and the output is still:
Function 1 in module1
Function 2 in module2
This shows that the pyc file can indeed exist independently and be executed by the Python interpreter.
9. Decompilation of pyc file
Although pyc files can prevent source code leakage to some extent, they can still be decompiled. According to the opcode provided in the Python source code, the py file source code can be decompiled based on the pyc file.
You can find some decompilation tools on the Internet, such as uncompyle6, which can be used to decompile pyc files. However, it should be noted that the compiled pyc files by different versions are different, and the decompilation tool may only support specific versions of pyc files.
10. Summary
The pyc file is a binary bytecode file of Python and is generated after compilation of the py file. The existence of pyc files can improve the running efficiency of Python programs, prevent source code leakage, and realize cross-platform deployment. Understanding the generation mechanism and usage methods of pyc files is of great significance to optimizing Python program performance, protecting source code, and cross-platform deployment.
Through the introduction of this article, I believe you have a deep understanding of pyc files. In actual development, pyc files can be used reasonably as needed.
The above is a detailed explanation of the Python pyc file in detail. For more information about Python pyc files, please follow my other related articles!