[issue32668] deepcopy() fails on ArgumentParser instances

[Terry J. Reedy]

Terry J. Reedy  added the comment:

Hi, you seem to be in luck, regardless of version.

Python 3.7.0a4+ (heads/master:a49ac99029, Jan 27 2018, 00:11:50) [MSC v.1900 32 
bit (Intel)] on win32
Type "help", "copyright", "credits" or "license" for more information.
>>> import argparse
>>> from copy import deepcopy
>>> parser = argparse.ArgumentParser()
>>> deepcopy(parser)
ArgumentParser(prog='', usage=None, description=None, formatter_class=, conflict_handler='error', add_help=True)

Fresh 3.6.4+ build also runs, but without enhanced repr.
...


(Note: 'crash' here means segfault rather than Python exception.)

--
nosy: +terry.reedy
resolution:  -> out of date
stage:  -> resolved
status: open -> closed
type: crash -> behavior

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[issue32668] deepcopy() fails on ArgumentParser instances

[Nitish]

Nitish  added the comment:

This seems to have been fixed in the latest master.

Commit I tested: 37420deb80dcf0fc41a728838b0340b93ca01d90

--
nosy: +nitishch

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[issue32668] deepcopy() fails on ArgumentParser instances

[Martin Kolman]

New submission from Martin Kolman :

We (the Anaconda OS intaller team) are in the process of switching to a new 
version of a library (Pykickstart), which among other things switched from 
using optparse to argparse. And during this endeavour we found that it's 
apparently not possible to deepcopy ArgumentParser instances:


$ ipython3
Python 3.6.3 (default, Oct  9 2017, 12:07:10) 
Type 'copyright', 'credits' or 'license' for more information
IPython 6.2.1 -- An enhanced Interactive Python. Type '?' for help.

In [1]: import argparse

In [2]: from copy import deepcopy

In [3]: parser = argparse.ArgumentParser()

In [4]: deepcopy(parser)
---
TypeError Traceback (most recent call last)
 in ()
> 1 deepcopy(parser)

/usr/lib64/python3.6/copy.py in deepcopy(x, memo, _nil)
178 y = x
179 else:
--> 180 y = _reconstruct(x, memo, *rv)
181 
182 # If is its own copy, don't memoize.

/usr/lib64/python3.6/copy.py in _reconstruct(x, memo, func, args, state, 
listiter, dictiter, deepcopy)
278 if state is not None:
279 if deep:
--> 280 state = deepcopy(state, memo)
281 if hasattr(y, '__setstate__'):
282 y.__setstate__(state)

/usr/lib64/python3.6/copy.py in deepcopy(x, memo, _nil)
148 copier = _deepcopy_dispatch.get(cls)
149 if copier:
--> 150 y = copier(x, memo)
151 else:
152 try:

/usr/lib64/python3.6/copy.py in _deepcopy_dict(x, memo, deepcopy)
238 memo[id(x)] = y
239 for key, value in x.items():
--> 240 y[deepcopy(key, memo)] = deepcopy(value, memo)
241 return y
242 d[dict] = _deepcopy_dict

/usr/lib64/python3.6/copy.py in deepcopy(x, memo, _nil)
148 copier = _deepcopy_dispatch.get(cls)
149 if copier:
--> 150 y = copier(x, memo)
151 else:
152 try:

/usr/lib64/python3.6/copy.py in _deepcopy_list(x, memo, deepcopy)
213 append = y.append
214 for a in x:
--> 215 append(deepcopy(a, memo))
216 return y
217 d[list] = _deepcopy_list

/usr/lib64/python3.6/copy.py in deepcopy(x, memo, _nil)
178 y = x
179 else:
--> 180 y = _reconstruct(x, memo, *rv)
181 
182 # If is its own copy, don't memoize.

/usr/lib64/python3.6/copy.py in _reconstruct(x, memo, func, args, state, 
listiter, dictiter, deepcopy)
278 if state is not None:
279 if deep:
--> 280 state = deepcopy(state, memo)
281 if hasattr(y, '__setstate__'):
282 y.__setstate__(state)

/usr/lib64/python3.6/copy.py in deepcopy(x, memo, _nil)
148 copier = _deepcopy_dispatch.get(cls)
149 if copier:
--> 150 y = copier(x, memo)
151 else:
152 try:

/usr/lib64/python3.6/copy.py in _deepcopy_dict(x, memo, deepcopy)
238 memo[id(x)] = y
239 for key, value in x.items():
--> 240 y[deepcopy(key, memo)] = deepcopy(value, memo)
241 return y
242 d[dict] = _deepcopy_dict

/usr/lib64/python3.6/copy.py in deepcopy(x, memo, _nil)
178 y = x
179 else:
--> 180 y = _reconstruct(x, memo, *rv)
181 
182 # If is its own copy, don't memoize.

/usr/lib64/python3.6/copy.py in _reconstruct(x, memo, func, args, state, 
listiter, dictiter, deepcopy)
278 if state is not None:
279 if deep:
--> 280 state = deepcopy(state, memo)
281 if hasattr(y, '__setstate__'):
282 y.__setstate__(state)

/usr/lib64/python3.6/copy.py in deepcopy(x, memo, _nil)
148 copier = _deepcopy_dispatch.get(cls)
149 if copier:
--> 150 y = copier(x, memo)
151 else:
152 try:

/usr/lib64/python3.6/copy.py in _deepcopy_dict(x, memo, deepcopy)
238 memo[id(x)] = y
239 for key, value in x.items():
--> 240 y[deepcopy(key, memo)] = deepcopy(value, memo)
241 return y
242 d[dict] = _deepcopy_dict

/usr/lib64/python3.6/copy.py in deepcopy(x, memo, _nil)
159 copier = getattr(x, "__deepcopy__", None)
160 if copier:
--> 161 y = copier(memo)
162 else:
163 reductor = dispatch_table.get(cls)

TypeError: cannot deepcopy this pattern object


This should either be fixed or documented in proper places (the argparse 
documentation does not mention any pottential deepcopy issues as far as we can 
tell).

--
components: Library (Lib)
messages: 310686
nosy: mkolman
priority: normal
severity: normal
status: open
title: deepcopy() fails on ArgumentParser instances
type: crash
versions: Python 3.6

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