普通列表和 dict.items() 之间的区别

Question

help(difflib.get_close_matches)
Help on function get_close_matches in module difflib:

get_close_matches(word, possibilities, n=3, cutoff=0.6)
Use SequenceMatcher to return list of the best "good enough" matches.

word is a sequence for which close matches are desired (typically a
string).
possibilities is a list of sequences against which to match              
word(typically a list of strings).

I can use dict.keys() as the parameter "possibilities" in get_close_matches where "possibilities" expects a list. But why i can't access dict.items() as a normal list like a[0], a[1] (a is a list) ?

Answer 1

In Python 3, dict.items() (and also .keys() and .values() ) returns a special dictionary view object . It behaves like an iterator, but isn't specifically a list.

#!/usr/bin/env python3
d = {}
d['a'] = 1
d['b'] = 2

# You can pack items() into a list and then it's a "real" list    
l = list(d.items())
print(repr(l[1]))

# Or you can use itertools or otherwise use it as a plain iterator
import itertools
for p in itertools.islice(d.items(), 1, 2):
  print(repr(p))

Answer 2

Dict.items() doesn't return a list. Instead it returns a class of dict_items. If you are interested about the keys alone use Dict.keys(). You cannot access the dictionary using index approach