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Add drop_by_id method to shell, to remove variables added by extensions. #889

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This was prompted by the revived physics extension. Extensions can drop a lot of variables into the user namespace. Ideally, if the extension is unloaded, those variables should disappear, but only if the names haven't been rebound.

This works as a counterpart to ip.push(). The idea is that an extension can work like this:

myvars = dict(a=foo(), b=bar(), c=baz())

def load_ipython_extension(ip):

def unload_ipython_extension(ip):

merged with rebase to avoid recursive merge for just one commit. thx!

@fperez fperez closed this
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18 IPython/core/
@@ -1264,6 +1264,24 @@ def push(self, variables, interactive=True):
for name,val in vdict.iteritems():
config_ns[name] = val
+ def drop_by_id(self, variables):
+ """Remove a dict of variables from the user namespace, if they are the
+ same as the values in the dictionary.
+ This is intended for use by extensions: variables that they've added can
+ be taken back out if they are unloaded, without removing any that the
+ user has overwritten.
+ Parameters
+ ----------
+ variables : dict
+ A dictionary mapping object names (as strings) to the objects.
+ """
+ for name, obj in variables.iteritems():
+ if name in self.user_ns and self.user_ns[name] is obj:
+ del self.user_ns[name]
+ self.user_ns_hidden.pop(name, None)
# Things related to object introspection
15 IPython/core/tests/
@@ -179,4 +179,17 @@ def test_bad_custom_tb_return(self):
io.stderr = save_stderr
+ def test_drop_by_id(self):
+ ip = get_ipython()
+ myvars = {"a":object(), "b":object(), "c": object()}
+ ip.push(myvars, interactive=False)
+ for name in myvars:
+ assert name in ip.user_ns, name
+ assert name in ip.user_ns_hidden, name
+ ip.user_ns['b'] = 12
+ ip.drop_by_id(myvars)
+ for name in ["a", "c"]:
+ assert name not in ip.user_ns, name
+ assert name not in ip.user_ns_hidden, name
+ assert ip.user_ns['b'] == 12
+ ip.reset()
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