Understanding PyInstaller Hooks

In summary, a “hook” file extends PyInstaller to adapt it to the special needs and methods used by a Python package. The word “hook” is used for two kinds of files. A runtime hook helps the bootloader to launch an app. For more on runtime hooks, see Changing Runtime Behavior. Other hooks run while an app is being analyzed. They help the Analysis phase find needed files.

The majority of Python packages use normal methods of importing their dependencies, and PyInstaller locates all their files without difficulty. But some packages make unusual uses of the Python import mechanism, or make clever changes to the import system at runtime. For this or other reasons, PyInstaller cannot reliably find all the needed files, or may include too many files. A hook can tell about additional source files or data files to import, or files not to import.

A hook file is a Python script, and can use all Python features. It can also import helper methods from PyInstaller.utils.hooks and useful variables from PyInstaller.compat. These helpers are documented below.

The name of a hook file is hook-full-import-name.py, where full-import-name is the fully-qualified name of an imported script or module. You can browse through the existing hooks in the hooks folder of the PyInstaller distribution folder and see the names of the packages for which hooks have been written. For example hook-PyQt5.QtCore.py is a hook file telling about hidden imports needed by the module PyQt5.QtCore. When your script contains import PyQt5.QtCore (or from PyQt5 import QtCore), Analysis notes that hook-PyQt5.QtCore.py exists, and will call it.

Many hooks consist of only one statement, an assignment to hiddenimports. For example, the hook for the dnspython package, called hook-dns.rdata.py, has only this statement:

hiddenimports = [

When Analysis sees import dns.rdata or from dns import rdata it calls hook-dns.rdata.py and examines its value of hiddenimports. As a result, it is as if your source script also contained:

import dns.rdtypes.*
import dsn.rdtypes.ANY.*

A hook can also cause the addition of data files, and it can cause certain files to not be imported. Examples of these actions are shown below.

When the module that needs these hidden imports is useful only to your project, store the hook file(s) somewhere near your source file. Then specify their location to the pyinstaller or pyi-makespec command with the --additional-hooks-dir= option. If the hook file(s) are at the same level as the script, the command could be simply:

pyinstaller --additional-hooks-dir=. myscript.py

If you write a hook for a module used by others, please send us the hook file so we can make it available.

How a Hook Is Loaded

A hook is a module named hook-full-import-name.py in a folder where the Analysis object looks for hooks. Each time Analysis detects an import, it looks for a hook file with a matching name. When one is found, Analysis imports the hook’s code into a Python namespace. This results in the execution of all top-level statements in the hook source, for example import statements, assignments to global names, and function definitions. The names defined by these statements are visible to Analysis as attributes of the namespace.

Thus a hook is a normal Python script and can use all normal Python facilities. For example it could test sys.version and adjust its assignment to hiddenimports based on that. There are over 150 hooks in the PyInstaller installation. You are welcome to browse through them for examples.

Hook Global Variables

A majority of the existing hooks consist entirely of assignments of values to one or more of the following global variables. If any of these are defined by the hook, Analysis takes their values and applies them to the bundle being created.


A list of module names (relative or absolute) that should be part of the bundled app. This has the same effect as the --hidden-import command line option, but it can contain a list of names and is applied automatically only when the hooked module is imported. Example:

hiddenimports = ['_proxy', 'utils', 'defs']

A list of absolute module names that should not be part of the bundled app. If an excluded module is imported only by the hooked module or one of its sub-modules, the excluded name and its sub-modules will not be part of the bundle. (If an excluded name is explicitly imported in the source file or some other module, it will be kept.) Several hooks use this to prevent automatic inclusion of the tkinter module. Example:

excludedimports = [modname_tkinter]

A list of files to bundle with the app as data. Each entry in the list is a tuple containing two strings. The first string specifies a file (or file “glob”) in this system, and the second specifies the name(s) the file(s) are to have in the bundle. (This is the same format as used for the datas= argument, see Adding Data Files.) Example:

datas = [ ('/usr/share/icons/education_*.png', 'icons') ]

If you need to collect multiple directories or nested directories, you can use helper functions from the PyInstaller.utils.hooks module (see below) to create this list, for example:

datas = collect_data_files('submodule1')
datas+= collect_data_files('submodule2')

In rare cases you may need to apply logic to locate particular files within the file system, for example because the files are in different places on different platforms or under different versions. Then you can write a hook() function as described below under The hook(hook_api) Function.


A list of files or directories to bundle as binaries. The format is the same as datas (tuples with strings that specify the source and the destination). Binaries is a special case of datas, in that PyInstaller will check each file to see if it depends on other dynamic libraries. Example:

binaries = [ ('C:\\Windows\\System32\\*.dll', 'dlls') ]

Many hooks use helpers from the PyInstaller.utils.hooks module to create this list (see below):

binaries = collect_dynamic_libs('zmq')

Useful Items in PyInstaller.compat

A hook may import the following names from PyInstaller.compat, for example:

from PyInstaller.compat import modname_tkinter, is_win
True when the active Python is version 2.7.
True when the active Python is version 3.X.
is_py34, is_py35, is_py36:
True when the current version of Python is at least 3.4, 3.5 or 3.6 respectively.
True in a Windows system.
True when sys.platform=='cygwin'.
True in Mac OS X.
True in any Linux system (sys.platform.startswith('linux')).
True in Solaris.
True in AIX.
True in FreeBSD.
True in any virtual environment (either virtualenv or venv).
String, the correct path to the base Python installation, whether the installation is native or a virtual environment.

String, Tkinter in Python 2.7 but tkinter in Python 3. To prevent an unnecessary import of Tkinter, write:

from PyInstaller.compat import modname_tkinter
excludedimports = [ modname_tkinter ]
List of Python C-extension file suffixes. Used for finding all binary dependencies in a folder; see hook-cryptography.py for an example.

Useful Items in PyInstaller.utils.hooks

A hook may import useful functions from PyInstaller.utils.hooks. Use a fully-qualified import statement, for example:

from PyInstaller.utils.hooks import collect_data_files, eval_statement

The PyInstaller.utils.hooks functions listed here are generally useful and used in a number of existing hooks. There are several more functions besides these that serve the needs of specific hooks, such as hooks for PyQt4/5. You are welcome to read the PyInstaller.utils.hooks module (and read the existing hooks that import from it) to get code and ideas.

exec_statement( 'statement' ):

Execute a single Python statement in an externally-spawned interpreter and return the standard output that results, as a string. Examples:

tk_version = exec_statement(
   "from _tkinter import TK_VERSION; print(TK_VERSION)"

mpl_data_dir = exec_statement(
   "import matplotlib; print(matplotlib._get_data_path())"
datas = [ (mpl_data_dir, "") ]
eval_statement( 'statement' ):

Execute a single Python statement in an externally-spawned interpreter. If the resulting standard output text is not empty, apply the eval() function to it; else return None. Example:

databases = eval_statement('''
   import sqlalchemy.databases
for db in databases:
   hiddenimports.append("sqlalchemy.databases." + db)
is_module_satisfies( requirements, version=None, version_attr='__version__' ):

Check that the named module (fully-qualified) exists and satisfies the given requirement. Example:

if is_module_satisfies('sqlalchemy >= 0.6'):

This function provides robust version checking based on the same low-level algorithm used by easy_install and pip, and should always be used in preference to writing your own comparison code. In particular, version strings should never be compared lexicographically (except for exact equality). For example '00.5' > '0.6' returns True, which is not the desired result.

The requirements argument uses the same syntax as supported by the Package resources module of setup tools (follow the link to see the supported syntax).

The optional version argument is is a PEP0440-compliant, dot-delimited version specifier such as '3.14-rc5'.

When the package being queried has been installed by easy_install or pip, the existing setup tools machinery is used to perform the test and the version and version_attr arguments are ignored.

When that is not the case, the version argument is taken as the installed version of the package (perhaps obtained by interrogating the package in some other way). When version is None, the named package is imported into a subprocess, and the __version__ value of that import is tested. If the package uses some other name than __version__ for its version global, that name can be passed as the version_attr argument.

For more details and examples refer to the function’s doc-string, found in Pyinstaller/utils/hooks/__init__.py.

collect_submodules( 'package-name', pattern=None ):

Returns a list of strings that specify all the modules in a package, ready to be assigned to the hiddenimports global. Returns an empty list when package does not name a package (a package is defined as a module that contains a __path__ attribute).

The pattern, if given, is function to filter through the submodules found, selecting which should be included in the returned list. It takes one argument, a string, which gives the name of a submodule. Only if the function returns true is the given submodule is added to the list of returned modules. For example, filter=lambda name: 'test' not in name will return modules that don’t contain the word test.

is_module_or_submodule( name, mod_or_submod ):
This helper function is designed for use in the filter argument of collect_submodules, by returning True if the given name is a module or a submodule of mod_or_submod. For example: collect_submodules('foo', lambda name: not is_module_or_submodule(name, 'foo.test')) excludes foo.test and foo.test.one but not foo.testifier.
collect_data_files( 'module-name', subdir=None, include_py_files=False ):

Returns a list of (source, dest) tuples for all non-Python (i.e. data) files found in module-name, ready to be assigned to the datas global. module-name is the fully-qualified name of a module or package (but not a zipped “egg”). The function uses os.walk() to visit the module directory recursively. subdir, if given, restricts the search to a relative subdirectory.

Normally Python executable files (ending in .py, .pyc, etc.) are not collected. Pass include_py_files=True to collect those files as well. (This can be used with routines such as those in pkgutil that search a directory for Python executable files and load them as extensions or plugins.)

collect_dynamic_libs( 'module-name' ):

Returns a list of (source, dest) tuples for all the dynamic libs present in a module directory. The list is ready to be assigned to the binaries global variable. The function uses os.walk() to examine all files in the module directory recursively. The name of each file found is tested against the likely patterns for a dynamic lib: *.dll, *.dylib, lib*.pyd, and lib*.so. Example:

binaries = collect_dynamic_libs( 'enchant' )
get_module_file_attribute( 'module-name' ):

Return the absolute path to module-name, a fully-qualified module name. Example:

nacl_dir = os.path.dirname(get_module_file_attribute('nacl'))
get_package_paths( 'package-name' ):

Given the name of a package, return a tuple. The first element is the absolute path to the folder where the package is stored. The second element is the absolute path to the named package. For example, if pkg.subpkg is stored in /abs/Python/lib the result of:

get_package_paths( 'pkg.subpkg' )

is the tuple, ( '/abs/Python/lib', '/abs/Python/lib/pkg/subpkg' )

copy_metadata( 'package-name' ):

Given the name of a package, return the name of its distribution metadata folder as a list of tuples ready to be assigned (or appended) to the datas global variable.

Some packages rely on metadata files accessed through the pkg_resources module. Normally PyInstaller does not include these metadata files. If a package fails without them, you can use this function in a hook file to easily add them to the bundle. The tuples in the returned list have two strings. The first is the full pathname to a folder in this system. The second is the folder name only. When these tuples are added to datas, the folder will be bundled at the top level. If package-name does not have metadata, an AssertionError exception is raised.

get_homebrew_path( formula='' ):
Return the homebrew path to the named formula, or to the global prefix when formula is omitted. Returns None if not found.
Return the path to the top-level Python package containing the Django files, or None if nothing can be found.
django_dottedstring_imports( 'django-root-dir' )
Return a list of all necessary Django modules specified in the Django settings.py file, such as the Django.settings.INSTALLED_APPS list and many others.

The hook(hook_api) Function

In addition to, or instead of, setting global values, a hook may define a function hook(hook_api). A hook() function should only be needed if the hook needs to apply sophisticated logic or to make a complex search of the source machine.

The Analysis object calls the function and passes it a hook_api object which has the following immutable properties:

The fully-qualified name of the module that caused the hook to be called, e.g., six.moves.tkinter.

The absolute path of the module. If it is:

  • A standard (rather than namespace) package, this is the absolute path of this package’s directory.
  • A namespace (rather than standard) package, this is the abstract placeholder -.
  • A non-package module or C extension, this is the absolute path of the corresponding file.
A list of the absolute paths of all directories comprising the module if it is a package, or None. Typically the list contains only the absolute path of the package’s directory.

The hook_api object also offers the following methods:

add_imports( *names ):
The names argument may be a single string or a list of strings giving the fully-qualified name(s) of modules to be imported. This has the same effect as adding the names to the hiddenimports global.
del_imports( *names ):
The names argument may be a single string or a list of strings, giving the fully-qualified name(s) of modules that are not to be included if they are imported only by the hooked module. This has the same effect as adding names to the excludedimports global.
add_datas( tuple_list ):
The tuple_list argument has the format used with the datas global variable. This call has the effect of adding items to that list.
add_binaries( tuple_list ):
The tuple_list argument has the format used with the binaries global variable. This call has the effect of adding items to that list.

The hook() function can add, remove or change included files using the above methods of hook_api. Or, it can simply set values in the four global variables, because these will be examined after hook() returns.

The pre_find_module_path( pfmp_api ) Method

You may write a hook with the special function pre_find_module_path( pfmp_api ). This method is called when the hooked module name is first seen by Analysis, before it has located the path to that module or package (hence the name “pre-find-module-path”).

Hooks of this type are only recognized if they are stored in a sub-folder named pre_find_module_path in a hooks folder, either in the distributed hooks folder or an --additional-hooks-dir folder. You may have normal hooks as well as hooks of this type for the same module. For example PyInstaller includes both a hooks/hook-distutils.py and also a hooks/pre_find_module_path/hook-distutils.py.

The pfmp_api object that is passed has the following immutable attribute:

A string, the fully-qualified name of the hooked module.

The pfmp_api object has one mutable attribute, search_dirs. This is a list of strings that specify the absolute path, or paths, that will be searched for the hooked module. The paths in the list will be searched in sequence. The pre_find_module_path() function may replace or change the contents of pfmp_api.search_dirs.

Immediately after return from pre_find_module_path(), the contents of search_dirs will be used to find and analyze the module.

For an example of use, see the file hooks/pre_find_module_path/hook-distutils.py. It uses this method to redirect a search for distutils when PyInstaller is executing in a virtual environment.

The pre_safe_import_module( psim_api ) Method

You may write a hook with the special function pre_safe_import_module( psim_api ). This method is called after the hooked module has been found, but before it and everything it recursively imports is added to the “graph” of imported modules. Use a pre-safe-import hook in the unusual case where:

  • The script imports package.dynamic-name
  • The package exists
  • however, no module dynamic-name exists at compile time (it will be defined somehow at run time)

You use this type of hook to make dynamically-generated names known to PyInstaller. PyInstaller will not try to locate the dynamic names, fail, and report them as missing. However, if there are normal hooks for these names, they will be called.

Hooks of this type are only recognized if they are stored in a sub-folder named pre_safe_import_module in a hooks folder, either in the distributed hooks folder or an --additional-hooks-dir folder. (See the distributed hooks/pre_safe_import_module folder for examples.)

You may have normal hooks as well as hooks of this type for the same module. For example the distributed system has both a hooks/hook-gi.repository.GLib.py and also a hooks/pre_safe_import_module/hook-gi.repository.GLib.py.

The psim_api object offers the following attributes, all of which are immutable (an attempt to change one raises an exception):

String, the unqualified name of the hooked module, for example text.
String, the fully-qualified name of the hooked module, for example email.mime.text.
The module graph representing all imports processed so far.
If this module is a top-level module of its package, None. Otherwise, the graph node that represents the import of the top-level module.

The last two items, module_graph and parent_package, are related to the module-graph, the internal data structure used by PyInstaller to document all imports. Normally you do not need to know about the module-graph.

The psim_api object also offers the following methods:

add_runtime_module( fully_qualified_name ):

Use this method to add an imported module whose name may not appear in the source because it is dynamically defined at run-time. This is useful to make the module known to PyInstaller and avoid misleading warnings. A typical use applies the name from the psim_api:

psim_api.add_runtime_module( psim_api.module_name )
add_alias_module( real_module_name, alias_module_name ):
real_module_name is the fully-qualifed name of an existing module, one that has been or could be imported by name (it will be added to the graph if it has not already been imported). alias_module_name is a name that might be referenced in the source file but should be treated as if it were real_module_name. This method ensures that if PyInstaller processes an import of alias_module_name it will use real_module_name.
append_package_path( directory ):
The hook can use this method to add a package path to be searched by PyInstaller, typically an import path that the imported module would add dynamically to the path if the module was executed normally. directory is a string, a pathname to add to the __path__ attribute.