New submission from David M. Beazley <beaz...@users.sourceforge.net>:
The json module is described as having an interface similar to pickle:
json.dump()
json.dumps()
json.load()
json.loads()
I think it would be a WISE idea to add a huge warning message to the
documentation that these functions should *NOT* be used to serialize or
unserialize multiple objects on the same file stream like pickle. For
example:
f = open("stuff","w")
json.dump(obj1, f)
json.dump(obj2, f) # NO! FLAMING DEATH!
f = open("stuff","r")
obj1 = json.load(f)
obj2 = json.load(f) # NO! EXTRA CRIPSY FLAMING DEATH!
For one, it doesn't work. load() actually reads the whole file into a
big string and tries to parse it as a single object. If there are
multiple objects in the file, you get a nasty exeption. Second, I'm
not even sure this is technically allowed by the JSON spec.
As far as I call tell, concatenating JSON objects together in the same
file falls into the same category as concatenating two HTML documents
together in the same file (something you just don't do).
Related: json.load() should probably not be used on any streaming input
source such as a file wrapped around a socket. The first thing it does
is consume the entire input by calling f.read()---which probably not
what someone is expecting (and it might even cause the whole program to
hang).
----------
assignee: georg.brandl
components: Documentation
messages: 78547
nosy: beazley, georg.brandl
severity: normal
status: open
title: json documentation needs a BAWM (Big A** Warning Message)
type: behavior
versions: Python 2.6, Python 3.0
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Python tracker <rep...@bugs.python.org>
<http://bugs.python.org/issue4783>
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