Re: Using dicts and lists as default arguments of functions

[MRAB]

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['1'] = 1
    print 2, a

def tstb(a=None):
    if a is None:
        a = []
    print 1, a
    a.append(1)
    print 2, a


It's all explained here:

    http://effbot.org/zone/default-values.htm
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