Johan a écrit :
Dear all,
Considering this test program:
def tst(a={}):
Stop here, we already know what will follow !-)
And yes, it's one of Python's most (in)famous gotchas : default
arguments values are computed only once, at function definition time
(that is, when the def statement is e
Johan wrote:
Dear all,
Considering this test program:
def tst(a={}):
print 1, a
a['1'] = 1
print 2, a
del a
def tstb(a=[]):
print 1, a
a.append(1)
print 2, a
del a
[snip]
Do this instead:
def tst(a=None):
if a is None:
a = {}
print 1, a
a[
Johan wrote:
> Dear all,
>
> Considering this test program:
>
> def tst(a={}):
> print 1, a
> a['1'] = 1
> print 2, a
> del a
The idiom to use is
def tst (a=None):
if a is None:
a = {}
# ...
and so on. This means that every call to tst with unspecified a
Dear all,
Considering this test program:
def tst(a={}):
print 1, a
a['1'] = 1
print 2, a
del a
def tstb(a=[]):
print 1, a
a.append(1)
print 2, a
del a
tst()
tst()
tstb()
tstb()
With output:
t...@tnjx:~/tst> python tt.py
1 {}
2 {'1': 1}
1 {'1': 1}
2 {'1': 1}
