我不禁想知道为什么Python生成的ELF与原始源代码相比相当大。让我们来看看最简单的代码helloworld。
user@linux:~/Python$ cat hello.py
print('Hello, World!')
user@linux:~/Python$
使用pyinstaller 转换为ELF
user@linux:~/Python$ pyinstaller -F hello.py
48 INFO: PyInstaller: 3.4
49 INFO: Python: 3.6.7
50 INFO: Platform: Linux-4.15.0-38-generic-x86_64-with-Ubuntu-18.04-bionic
50 INFO: wrote /home/user/Python/hello.spec
53 INFO: UPX is not available.
54 INFO: Extending PYTHONPATH with paths
['/home/user/Python', '/home/user/Python']
55 INFO: checking Analysis
60 INFO: Building because _python_version changed
60 INFO: Initializing module dependency graph...
62 INFO: Initializing module graph hooks...
64 INFO: Analyzing base_library.zip ...
3061 INFO: running Analysis Analysis-00.toc
3096 INFO: Caching module hooks...
3100 INFO: Analyzing /home/user/Python/hello.py
3103 INFO: Loading module hooks...
3104 INFO: Loading module hook "hook-encodings.py"...
3169 INFO: Loading module hook "hook-pydoc.py"...
3170 INFO: Loading module hook "hook-xml.py"...
3388 INFO: Looking for ctypes DLLs
3388 INFO: Analyzing run-time hooks ...
3394 INFO: Looking for dynamic libraries
3632 INFO: Looking for eggs
3633 INFO: Python library not in binary dependencies. Doing additional searching...
3684 INFO: Using Python library /usr/lib/x86_64-linux-gnu/libpython3.6m.so.1.0
3695 INFO: Warnings written to /home/user/Python/build/hello/warn-hello.txt
3717 INFO: Graph cross-reference written to /home/user/Python/build/hello/xref-hello.html
3722 INFO: checking PYZ
3725 INFO: Building because toc changed
3725 INFO: Building PYZ (ZlibArchive) /home/user/Python/build/hello/PYZ-00.pyz
4053 INFO: Building PYZ (ZlibArchive) /home/user/Python/build/hello/PYZ-00.pyz completed successfully.
4059 INFO: checking PKG
4064 INFO: Building because toc changed
4064 INFO: Building PKG (CArchive) PKG-00.pkg
6474 INFO: Building PKG (CArchive) PKG-00.pkg completed successfully.
6476 INFO: Bootloader /home/user/.local/lib/python3.6/site-packages/PyInstaller/bootloader/Linux-64bit/run
6477 INFO: checking EXE
6479 INFO: Rebuilding EXE-00.toc because hello missing
6480 INFO: Building EXE from EXE-00.toc
6481 INFO: Appending archive to ELF section in EXE /home/user/Python/dist/hello
6516 INFO: Building EXE from EXE-00.toc completed successfully.
user@linux:~/Python$
新ELF格式
user@linux:~/Python/dist$ ./hello
Hello, World!
user@linux:~/Python/dist$
user@linux:~/Python$ ls -lh hello.py
-rw-rw-r-- 1 user user 23 Dis 27 21:43 hello.py
user@linux:~/Python$
user@linux:~/Python/dist$ ls -lh hello
-rwxr-xr-x 1 user user 5.3M Dis 27 21:48 hello
user@linux:~/Python/dist$
正如您所看到的，原始代码只有23个字节，而ELF要大得多。。。5点30分！！！
让我们看看另一个使用C.的例子
user@linux:~/C$ cat hello.c
#include<stdio.h>
int main()
{
printf("Hello C Worldn");
}
user@linux:~/C$
user@linux:~/C$ gcc hello.c -o helloC
user@linux:~/C$
user@linux:~/C$ ls -l helloC
-rwxrwxr-x 1 user user 8304 Dis 27 21:53 helloC
user@linux:~/C$
user@linux:~/C$ ./helloC
Hello C World
user@linux:~/C$
user@linux:~/C$ ls -l hello.c
-rw-rw-r-- 1 user user 65 Dis 27 21:52 hello.c
user@linux:~/C$
user@linux:~/C$ ls -lh helloC
-rwxrwxr-x 1 user user 8.2K Dis 27 21:53 helloC
user@linux:~/C$
比较
Python code size = 27 bytes
Python ELF size = 5.3M
C code size = 65 bytes
C ELF size = 8.2K
有没有办法缩小尺寸？
因为Python不会编译成机器代码。
PyInstaller创建的ELF就像您的代码用所有必要的Python运行时文件打包一样简单。它在任何方面都无法与从C编译的二进制文件相比，后者包含机器代码和动态链接库(例如libc.so)。
PyInstaller、py2exe和几乎任何其他项目都没有真正将Python文件"转换"为可执行文件，这只是将完整的Python解释器(在我的机器上仅为4.4 MB)、您的项目及其所需的所有依赖项(都编译为字节码，解释器运行)打包为一个自解压的可执行文件，因此，它至少和(压缩的)Python安装一样大是正常的。
除了Python解释器本身和大型本地依赖项(比如numpy、scipy、PyQt)之外，几乎任何东西在最终可执行文件大小中都不算什么。你可能有一个10KLOCPython项目，只要你不引入任何其他外部依赖，你就会发现最终的可执行文件大小不会受到显著影响。
gcc编译一个C文件是创建一个实际的可执行文件，其中包含调用printf所需的导入和机器代码；它是15个字节的文字字符串，只有几个字节用于设置堆栈帧和实际调用printf，其余的都是ELF头、导入表和各种链接器垃圾(即使只在上面执行strip -s也会减少2KB)。