>>> [a, b] = 2, 3 >>> (a, b) = 2, 3 >>> {a, b} = 2, 3 File " ", line 1 SyntaxError: can't assign to literal
That could be because sets aren't ordered (even though it looks odd in this context).
Python bug: Can assign [] = (), but not () = []
21–30 of 53 posts
Re: Python bug: Can assign [] = (), but not () = []
#22>>> [a, b] = 2, 3 >>> (a, b) = 2, 3 >>> {a, b} = 2, 3 File " ", line 1 SyntaxError: can't assign to literal
That could be because sets aren't ordered (even though it looks odd in this context).
I thought that at first too, but even then the exception seems spurious. It would be more inline with existing Python behavior to evaluate it as undefined/indeterminate assignment order (though this would be pretty useless).
>>> a, b, c, d = {1, 2, 3, 'a'}
>>> a
'a'
Regardless, it shouldn't be surprising when writing insane code, that the language starts acting insane. Python as a whole is pretty decent when it comes to handling syntactic edge cases.
Re: Python bug: Can assign [] = (), but not () = []
#23....__class__ # Python 3 only
Re: Python bug: Can assign [] = (), but not () = []
#24Re: Python bug: Can assign [] = (), but not () = []
#25Dave Beazley gave a talk showing this. See https://twitter.com/renfredxh/status/586653125970386945
Re: Python bug: Can assign [] = (), but not () = []
#26I can also do this, which is harmful. >>> True = False >>> False = True
Only in Python 2, since that is a backward-compatibility feature. (“False” and “True” used to be variables containing 0 and 1 before Python had true booleans, many ages ago.) Python 3 makes “True” and “False” be constant values, like “1” or “2”, like they should be.
Only constant for certain values of "constant". ;)
(https://gist.github.com/Jach/1208215 works in Python 3 too.)
Re: Python bug: Can assign [] = (), but not () = []
#27Earlier quoted context omitted.
Only in Python 2, since that is a backward-compatibility feature. (“False” and “True” used to be variables containing 0 and 1 before Python had true booleans, many ages ago.) Python 3 makes “True” and “False” be constant values, like “1” or “2”, like they should be.
Only constant for certain values of "constant". ;) ( https://gist.github.com/Jach/1208215 works in Python 3 too.)
After “import ctypes”, all bets are off.
Re: Python bug: Can assign [] = (), but not () = []
#28Re: Python bug: Can assign [] = (), but not () = []
#29This is a fun numpy quirk: >>> 'x'*3.5 Traceback (most recent call last): File " ", line 1, in TypeError: can't multiply sequence by non-int of type 'float' >>> import numpy as np >>> print 'x'*np.float64(3.5) xxx
I use R predominantly, so forgive the lack of adequate Python-ese. Is this behavior because numpy overloads the multiplication operation with a string as string repetition and then implicitly casts the float64 down to an integer of 3? I'm curious why this behavior manifests. When I get a chance I'll test 'xyz'*np.float(3.5)
It's "normal" in python for this to work with integers:
>>> "x" * 3
xxx
Re: Python bug: Can assign [] = (), but not () = []
#30Earlier quoted context omitted.
Python 3 removed this feature unfortunately.
>>> (False, True) = (True, False) >>> 1 if False else 0 1 >>> bool(0) == False False
In[2]: (True, False) = (False, True)
In[3]: True
Out[3]: False
In[4]: 1 if False else 0
Out[4]: 1
In[5]: 'yes' if bool(0) == False else 'no'
Out[5]: 'no'
In[6]: bool(0) == False
Out[6]: False