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%with / %endwith IPython extension
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# -*- coding: utf-8 -*-
"""
%with and %endwith magics.
"""
#-----------------------------------------------------------------------------
# Imports
#-----------------------------------------------------------------------------
import re
from IPython.core.error import UsageError
from IPython.core.magic import Magics, magics_class, line_magic
#-----------------------------------------------------------------------------
# Functions and classes
#-----------------------------------------------------------------------------
@magics_class
class WithMagics(Magics):
"""Provides the %with and %endwith magics."""
def __init__(self, shell):
super(WithMagics, self).__init__(shell)
self._re_with = re.compile(r'^(?P<code>.*)\s+as\s+(?P<name>[_A-Za-z][_A-Za-z0-9]*):$')
self._contexts = []
@line_magic('with')
def with_(self, line=''):
m = self._re_with.match(line)
if not m:
raise UsageError("Error parsing statement.")
code = m.group('code')
name = m.group('name')
shell = self.shell
context = eval(code, shell.user_global_ns, shell.user_ns)
obj = context.__enter__()
print("Context manager %s started" % name)
# Return value to the user
shell.user_ns[name] = obj
self._contexts.append((name, context))
@line_magic
def endwith(self, line=''):
name, context = self._contexts.pop()
print("Context manager %s ended" % name)
context.__exit__(None, None, None)
def load_ipython_extension(ip):
"""Load the extension in IPython."""
ip.register_magics(WithMagics)
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