Are there any applicable differences between dict.items()
and dict.iteritems()
?
From the Python docs:
dict.items()
: Return a copy of the dictionary’s list of (key, value) pairs.
dict.iteritems()
: Return an iterator over the dictionary’s (key, value) pairs.
If I run the code below, each seems to return a reference to the same object. Are there any subtle differences that I am missing?
#!/usr/bin/python
d={1:'one',2:'two',3:'three'}
print 'd.items():'
for k,v in d.items():
if d[k] is v: print '\tthey are the same object'
else: print '\tthey are different'
print 'd.iteritems():'
for k,v in d.iteritems():
if d[k] is v: print '\tthey are the same object'
else: print '\tthey are different'
Output:
d.items():
they are the same object
they are the same object
they are the same object
d.iteritems():
they are the same object
they are the same object
they are the same object
It's part of an evolution.
Originally, Python items()
built a real list of tuples and returned that. That could potentially take a lot of extra memory.
Then, generators were introduced to the language in general, and that method was reimplemented as an iterator-generator method named iteritems()
. The original remains for backwards compatibility.
One of Python 3’s changes is that items()
now return iterators, and a list is never fully built. The iteritems()
method is also gone, since items()
in Python 3 works like viewitems()
in Python 2.7.