When Things Go Wrong

The information above covers most normal uses of PyInstaller. However, the variations of Python and third-party libraries are endless and unpredictable. It may happen that when you attempt to bundle your app either PyInstaller itself, or your bundled app, terminates with a Python traceback. Then please consider the following actions in sequence, before asking for technical help.

Recipes and Examples for Specific Problems

The PyInstaller FAQ page has work-arounds for some common problems. Code examples for some advanced uses and some common problems are available on our PyInstaller Recipes page. Some of the recipes there include:

  • A more sophisticated way of collecting data files than the one shown above (Adding Files to the Bundle).
  • Bundling a typical Django app.
  • A use of a run-time hook to set the PyQt4 API level.
  • A workaround for a multiprocessing constraint under Windows.

and others. Many of these Recipes were contributed by users. Please feel free to contribute more recipes!

Finding out What Went Wrong

Build-time Messages

When the Analysis step runs, it produces error and warning messages. These display after the command line if the --log-level option allows it. Analysis also puts messages in a warnings file named build/name/warnname.txt in the work-path= directory.

Analysis creates a message when it detects an import and the module it names cannot be found. A message may also be produced when a class or function is declared in a package (an __init__.py module), and the import specifies package.name. In this case, the analysis can’t tell if name is supposed to refer to a submodule or package.

The “module not found” messages are not classed as errors because typically there are many of them. For example, many standard modules conditionally import modules for different platforms that may or may not be present.

All “module not found” messages are written to the build/name/warnname.txt file. They are not displayed to standard output because there are many of them. Examine the warning file; often there will be dozens of modules not found, but their absence has no effect.

When you run the bundled app and it terminates with an ImportError, that is the time to examine the warning file. Then see Helping PyInstaller Find Modules below for how to proceed.

Build-Time Dependency Graph

If you specify --log-level=DEBUG to the pyinstaller command, PyInstaller writes two files of data about dependencies into the build folder.

The file build/name/xref-name.html in the work-path= directory is an HTML file that lists the full contents of the import graph, showing which modules are imported by which. You can open it in any web browser. Find a module name, then keep clicking the “imported by” links until you find the top-level import that causes that module to be included.

The file build/name/graph-name.dot in the work-path= directory is a GraphViz input file. You can process it with the GraphViz command dot to produce a graphical display of the import dependencies.

These files are very large because even the simplest “hello world” Python program ends up including a large number of standard modules. For this reason the graph file is not very useful in this release.

Build-Time Python Errors

PyInstaller sometimes terminates by raising a Python exception. In most cases the reason is clear from the exception message, for example “Your system is not supported”, or “Pyinstaller requires at least Python 2.7”. Others clearly indicate a bug that should be reported.

One of these errors can be puzzling, however: IOError("Python library not found!") PyInstaller needs to bundle the Python library, which is the main part of the Python interpreter, linked as a dynamic load library. The name and location of this file varies depending on the platform in use. Some Python installations do not include a dynamic Python library by default (a static-linked one may be present but cannot be used). You may need to install a development package of some kind. Or, the library may exist but is not in a folder where PyInstaller is searching.

The places where PyInstaller looks for the python library are different in different operating systems, but /lib and /usr/lib are checked in most systems. If you cannot put the python library there, try setting the correct path in the environment variable LD_LIBRARY_PATH in Linux or DYLD_LIBRARY_PATH in OS X.

Getting Debug Messages

Giving the --debug option causes the bundled executable itself to write progress messages when it runs. This can be useful during development of a complex package, or when your app doesn’t seem to be starting, or just to learn how the runtime works.

Normally the debug progress messages go to standard output. If the --windowed option is used when bundling a Windows app, they are displayed as MessageBoxes. For a --windowed Mac OS app they are not displayed.

Remember to bundle without --debug for your production version. Users would find the messages annoying.

Getting Python’s Verbose Imports

You can also pass a -v (verbose imports) flag to the embedded Python interpreter (see Giving Run-time Python Options above). This can be extremely useful. It can be informative even with apps that are apparently working, to make sure that they are getting all imports from the bundle, and not leaking out to the local installed Python.

Python verbose and warning messages always go to standard output and are not visible when the --windowed option is used. Remember to not use this in the distributed program.

Helping PyInstaller Find Modules

Extending the Path

If Analysis recognizes that a module is needed, but cannot find that module, it is often because the script is manipulating sys.path. The easiest thing to do in this case is to use the --paths= option to list all the other places that the script might be searching for imports:

pyi-makespec --paths=/path/to/thisdir \
             --paths=/path/to/otherdir myscript.py

These paths will be noted in the spec file. They will be added to the current sys.path during analysis.

Listing Hidden Imports

If Analysis thinks it has found all the imports, but the app fails with an import error, the problem is a hidden import; that is, an import that is not visible to the analysis phase.

Hidden imports can occur when the code is using __import__ or perhaps exec or eval. Hidden imports can also occur when an extension module uses the Python/C API to do an import. When this occurs, Analysis can detect nothing. There will be no warnings, only an ImportError at run-time.

To find these hidden imports, build the app with the -v flag (Getting Python’s Verbose Imports above) and run it.

Once you know what modules are needed, you add the needed modules to the bundle using the --hidden-import= command option, or by editing the spec file, or with a hook file (see Understanding PyInstaller Hooks below).

Extending a Package’s __path__

Python allows a script to extend the search path used for imports through the __path__ mechanism. Normally, the __path__ of an imported module has only one entry, the directory in which the __init__.py was found. But __init__.py is free to extend its __path__ to include other directories. For example, the win32com.shell.shell module actually resolves to win32com/win32comext/shell/shell.pyd. This is because win32com/__init__.py appends ../win32comext to its __path__.

Because the __init__.py of an imported module is not actually executed during analysis, changes it makes to __path__ are not seen by PyInstaller. We fix the problem with the same hook mechanism we use for hidden imports, with some additional logic; see Understanding PyInstaller Hooks below.

Note that manipulations of __path__ hooked in this way apply only to the Analysis. At runtime all imports are intercepted and satisfied from within the bundle. win32com.shell is resolved the same way as win32com.anythingelse, and win32com.__path__ knows nothing of ../win32comext.

Once in a while, that’s not enough.

Changing Runtime Behavior

More bizarre situations can be accomodated with runtime hooks. These are small scripts that manipulate the environment before your main script runs, effectively providing additional top-level code to your script.

There are two ways of providing runtime hooks. You can name them with the option --runtime-hook=path-to-script.

Second, some runtime hooks are provided. At the end of an analysis, the names in the module list produced by the Analysis phase are looked up in loader/rthooks.dat in the PyInstaller install folder. This text file is the string representation of a Python dictionary. The key is the module name, and the value is a list of hook-script pathnames. If there is a match, those scripts are included in the bundled app and will be called before your main script starts.

Hooks you name with the option are executed in the order given, and before any installed runtime hooks. If you specify --runtime-hook=file1.py --runtime-hook=file2.py then the execution order at runtime will be:

  1. Code of file1.py.
  2. Code of file2.py.
  3. Any hook specified for an included module that is found in rthooks/rthooks.dat.
  4. Your main script.

Hooks called in this way, while they need to be careful of what they import, are free to do almost anything. One reason to write a run-time hook is to override some functions or variables from some modules. A good example of this is the Django runtime hook (see loader/rthooks/pyi_rth_django.py in the PyInstaller folder). Django imports some modules dynamically and it is looking for some .py files. However .py files are not available in the one-file bundle. We need to override the function django.core.management.find_commands in a way that will just return a list of values. The runtime hook does this as follows:

import django.core.management
def _find_commands(_):
    return """cleanup shell runfcgi runserver""".split()
django.core.management.find_commands = _find_commands

Getting the Latest Version

If you have some reason to think you have found a bug in PyInstaller you can try downloading the latest development version. This version might have fixes or features that are not yet at PyPI. You can download the latest stable version and the latest development version from the PyInstaller Downloads page.

You can also install the latest version of PyInstaller directly using pip:

pip install -e https://github.com/pyinstaller/pyinstaller/archive/develop.zip

Asking for Help

When none of the above suggestions help, do ask for assistance on the PyInstaller Email List.

Then, if you think it likely that you see a bug in PyInstaller, refer to the How to Report Bugs page.