CODEWITHSUNDEEP
pythonpackageoverridingpython-import
DavidK
DavidK

Reputation: 2564

Override a package method, when that method is internally imported within the package

If I import a package, let's say networkx.

How to override one method inside it so that it's the one called by every other function inside the package ?

Example :

import networkx as nx

def _draw_networkx_nodes(G, pos,
                        nodelist=None,
                        node_size=300,
                        node_color='r',
                        node_shape='o',
                        alpha=1.0,
                        cmap=None,
                        vmin=None,
                        vmax=None,
                        ax=None,
                        linewidths=None,
                        label=None,
                        **kwds):
     print 'OK'

nx.draw_networkx_nodes = _draw_networkx_nodes

G = nx.Graph()
G.add_edge('A','B')
nx.draw(G)

I want the method draw to call other methods that will call my overriden function

Upvotes: 2

Views: 185

Answers (1)

Jörn Hees
Jörn Hees

Reputation: 3428

This is a problem of how methods are called in python. You're patching the draw_networkx_nodes in the networkx top module, but it doesn't originate from that top-module: The networkx.draw method is imported from networkx.drawing.nx_pylab. This draw method down there locally calls draw_networkx which locally (still down in that file) calls draw_networkx_nodes. This is why modifying the alias that was imported in networkx/__init__.py doesn't work: it's never called internally.

So in other: If you want to patch a method of a library, see which sub-module it's originating from and patch it there.

So in this case:

In [6]: nx.drawing.nx_pylab.draw_networkx_nodes = _draw_networkx_nodes

In [7]: nx.draw(G)
OK

Upvotes: 1

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