【发布时间】：2018-12-27 14:06:03
【问题描述】：
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。我们来看看最简单的代码，hello world。
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$
新的 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$
如您所见，原始代码只有 23 个字节，而 ELF 方式要大得多...... 5.3M !!!
让我们看另一个 C 的例子。
user@linux:~/C$ cat hello.c
#include<stdio.h>
int main()
{
printf("Hello C World\n");
}
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
有没有办法让尺寸变小？
【问题讨论】：
-
因为 Python “可执行文件”包括整个 Python 解释器和 stdlib。基本上，C 示例只是多个 1 和 0。
-
“源代码大小”什么都没有。
-
@usr2564301：嗯，最终的可执行文件比压缩后的 27 个字节要大。 :-) 但是，是的，除非您的程序很大，否则脚本本身可能与“整个 Python 解释器”的固定开销相比显得苍白。
-
@ShadowRanger：另外，我对 C 的体验是完全相反的。我已经看到数兆字节的源代码被编译成非常小的可执行文件。