Compatibility Tools

Some packages require a little extra help to work nicely with PythonCall.

Some of these are "fixes" that are silently applied for you, and some are just extra functions to bridge a gap. We aim to keep these as minimal as possible.

Python standard library

Whenever a Python exception is displayed by Julia, sys.last_traceback and friends are set. This allows the post-mortem debugger pdb.pm() to work. Disable by setting PythonCall.CONFIG.auto_sys_last_traceback = false.

Julia standard library

Python objects can be serialised with the Serialization stdlib. This uses pickle library under the hood. You can opt into using dill instead by setting the environment variable JULIA_PYTHONCALL_PICKLE="dill".

Tabular data / Pandas

The abstract type PyTable is for wrapper types around Python tables, providing the Tables.jl interface. PyTable(x) is shorthand for pyconvert(PyTable, x).

The subtype PyPandasDataFrame wraps a pandas.DataFrame.

For example, if x is a pandas.DataFrame then PyTable(x) is a PyPandasDataFrame and DataFrame(PyTable(x)) is a DataFrame.

In the other direction, the following functions can be used to convert any Tables.jl-compatible table to a Python table.

PythonCall.Compat.pytable — Function

pytable(src, format=:pandas; ...)

Construct a Python table from the Tables.jl-compatible table src.

The format controls the type of the resulting table, and is one of:

:pandas: A pandas.DataFrame. Keyword arguments are passed to the DataFrame constructor.
:columns: A dict mapping column names to columns.
:rows: A list of rows, which are namedtuples.
:rowdicts: A list of rows, which are dicts.

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MatPlotLib / PyPlot / Seaborn

MatPlotLib figures can be shown with Julia's display mechanism, like display(fig) or display(mime, fig).

This means that if you return a figure from a Jupyter or Pluto notebook cell, it will be shown. You can call display(plt.gcf()) to display the current figure.

We also provide a simple MatPlotLib backend: mpl.use("module://juliacall.matplotlib"). Now you can call plt.show() to display the figure with Julia's display mechanism. You can specify the format like plt.show(format="png").

Python GUIs (including MatPlotLib)

Event loops

If for example you wish to use PyPlot in interactive mode (matplotlib.pyplot.ion()) then activating the correct event loop will allow it to work.

PythonCall.Compat.event_loop_on — Function

event_loop_on(g::Symbol; interval=0.04, fix=false)

Activate an event loop for the GUI framework g, so that the framework can run in the background of a Julia session.

The event loop runs every interval seconds. If fix is true and g is a Qt framework, then fix_qt_plugin_path is called.

Supported values of g (and the Python module they relate to) are: :pyqt4 (PyQt4), :pyqt5 (PyQt5), :pyside (PySide), :pyside2 (PySide2), :gtk (gtk), :gtk3 (gi), :wx (wx), :tkinter (tkinter).

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PythonCall.Compat.event_loop_off — Function

event_loop_off(g::Symbol)

Terminate the event loop g if it is running.

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Qt path fix

PythonCall.Compat.fix_qt_plugin_path — Function

fix_qt_plugin_path()

Try to set the QT_PLUGIN_PATH environment variable in Python, if not already set.

This fixes the problem that Qt does not know where to find its qt.conf file, because it always looks relative to sys.executable, which can be the Julia executable not the Python one when using this package.

If CONFIG.auto_fix_qt_plugin_path is true, then this is run automatically before PyQt4, PyQt5, PySide or PySide2 are imported.

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IPython

The juliacall IPython extension adds these features to your IPython session:

The line magic %julia code executes the given Julia code in-line.
The cell magic %%julia executes a cell of Julia code.
Julia's stdout and stderr are redirected to IPython.
Calling display(x) from Julia will display x in IPython.

The extension is experimental and unstable - the API can change at any time.

You can explicitly enable the extension with %load_ext juliacall, but it will automatically be loaded if juliacall is imported and IPython is detected. You can disable this behavior with an environment variable.

The %%julia cell magic can synchronise variables between Julia and Python by listing them on the first line:

In [1]: %load_ext juliacall

In [2]: x = 2

In [3]: y = 8

In [4]: %%julia x y z
   ...: z = "$x^$y = $(x^y)";
   ...:
   ...:

In [5]: z
Out[5]: '2^8 = 256'

Also see the IPython docs for more information on extensions.

Asynchronous Julia code (including Makie)

Asynchronous Julia code will not normally run while Python is executing, unless it is in a separate thread.

This can be fixed by calling jl.yield() periodically from Python code, allowing the Julia scheduler to run.

When working at the Python REPL, you may call juliacall.interactive() which will allow Julia async code to run while the prompt is showing. This will allow interactive plots such as Makie to work.