Introduction#

I have a use case where I want to convert my Python script to standalone executable so that I do not need to type python before it to run the script. On Linux, it is easy to achieve with the help of shebang. However, on Windows, it does not work. Then I thought I might convert the script to Windows executable.

We can use pyinstaller to convert python script to Windows executable files. You can install it with pip:

How to use pyinstaller#

The most simple way to run pyinstaller is to invoke it without options:

It will create a dist/my_script directory where the generated executable resides with other DLL files. This executable file can not run alone: it must rely on other DLL files.

To create a standalone executable, we can use --onefile option.

To build an executable which runs on command line and does not need a GUI windows, we can use the --console option.

We can then generate the executable with the following command:

pyinstaller --onefile --console my_script.py

The generated executable will be dist/my_script.exe.

Reduce the size of executable#

One problem is that the generated executable file is huge even if the script only contains a few lines of code.

Create a virtual environment#

According to post here, to reduce the size of the produced executable, we can create a clean virtual environment where only packages required for our script are installed.

In my case, after building the executable inside a virtual env, I have reduced the executable size from more than 200Mb to only 6Mb!

Using UPX#

An additional way to reduce executable size is to use UPX to compress files. You can download the UPX windows release file and extract it to a folder. When running the pyinstaller, you can use --upx-dir to include UPX support:

pyinstall --onefile --console --upx-dir=/path/to/upx-folder my_script.py

In the above command, you only need to specify the path of the directory containing upx.exe.

However, certain DLL files which is need by the executable should not be compressed by UPX. If they are compressed, you may encounter errors when you run the produced executable:

Error loading Python DLL 'C:\Users\ADMINI~1\AppData\Local\Temp\_MEI45442\python36.dll'.
LoadLibrary: The parameter is incorrect.

Those DLLs failing to load should not be compressed by UPX. You can add --upx-exclude option to pyinstaller when building the executable, and this options can be used multiple times to exclude several files. For example:

pyinstaller.exe --onefile --console --upx-dir=upx-3.95-win64\upx-3.95-win64\ --upx-exclude=python36.dll --upx-exclude=vcruntime140.dll my_script.py

After that, the executable file can run without errors.

References#

• Reduce executable size.
• How to use upx with pyinstaller.
• Error loading pythonxx.dll.