TypeError: first argument must be callable

问题

fs = codecs.open('grammar_new.txt', encoding='utf-8')
unidata=[]
d={}
fr=codecs.open('rule.txt', 'w')
for line in fs:
    line_data=line.split()
    for i in range(0,len(line_data)):
       unidata.append(line_data[i])


d = defaultdict(unidata)

while executing this code will generate error as d = defaultdict(unidata) TypeError: first argument must be callable..I want to store duplicate keys in dictionary

回答1:

The first argument to defaultdict must be callable. You've passed an instance of list which isn't callable. You want to pass the 'list' type instead.

Typical use would be something like:

d = defaultdict(list)
for k, v in something:
    d[k].append(v)

Based on the unidata you seem to have provided in your comment, I think you want:

>>> from collections import defaultdict
>>> unidata = [[u'NP--->', u'N_NNP'], [u'NP--->', u'N_NN_S_NU'], [u'NP--->', u'N_NNP'], [u'NP--->', u'N_NNP'], [u'VGF--->', u'V_VM_VF'], [u'NP--->', u'N_NN']]
>>> d = defaultdict(list)
>>> for k, v in unidata:
...     d[k].append(v)
... 
>>> d
defaultdict(<type 'list'>, {u'VGF--->': [u'V_VM_VF'], u'NP--->': [u'N_NNP', u'N_NN_S_NU', u'N_NNP', u'N_NNP', u'N_NN']})

回答2:

I want to store duplicate keys in dictionary

This is simply not possible. Keys in dictionaries are unique. I think what you want is this:

d = defaultdict(list)
with codecs.open('grammar_new.txt', encoding='utf-8') as f:
   for line in f:
      if len(line.rstrip()):
          key,value = line.rstrip().split()
          d[key].append(value)

print(d)

Now d will contain for each key a list that contains the corresponding values. Each key must be unique, but it can have any number of values, which can be duplicates.

来源：https://stackoverflow.com/questions/21422670/typeerror-first-argument-must-be-callable

标签

python

defaultdict