How to keep your original dict while adding counter
As I understand it, I know when I call the Counter
hidden dict. This dict includes the keys value, zero will disappear.
from collections import Counter
a = {"a": 1, "b": 5, "d": 0}
b = {"b": 1, "c": 2}
print Counter(a) + Counter(b)
If I want to keep my keys, how do I do it?
This is my expected output:
Counter({'b': 6, 'c': 2, 'a': 1, 'd': 0})
You can also use update()
Counter method instead of operator +
, example -
>>> a = {"a": 1, "b": 5, "d": 0}
>>> b = {"b": 1, "c": 2}
>>> x = Counter(a)
>>> x.update(Counter(b))
>>> x
Counter({'b': 6, 'c': 2, 'a': 1, 'd': 0})
update()
the function adds the number of samples instead of replacing them, and it does not remove the zero value. We can also do Counter(b)
and then update with Counter(a)
, Example -
>>> y = Counter(b)
>>> y.update(Counter(a))
>>> y
Counter({'b': 6, 'c': 2, 'a': 1, 'd': 0})
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Unfortunately, when adding two counters, only positive counter elements are used.
If you want to store zero-numbered elements, you can define a function like this:
def addall(a, b):
c = Counter(a) # copy the counter a, preserving the zero elements
for x in b: # for each key in the other counter
c[x] += b[x] # add the value in the other counter to the first
return c
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You can just subclass Counter
and customize its method __add__
:
from collections import Counter
class MyCounter(Counter):
def __add__(self, other):
"""Add counts from two counters.
Preserves counts with zero values.
>>> MyCounter('abbb') + MyCounter('bcc')
MyCounter({'b': 4, 'c': 2, 'a': 1})
>>> MyCounter({'a': 1, 'b': 0}) + MyCounter({'a': 2, 'c': 3})
MyCounter({'a': 3, 'c': 3, 'b': 0})
"""
if not isinstance(other, Counter):
return NotImplemented
result = MyCounter()
for elem, count in self.items():
newcount = count + other[elem]
result[elem] = newcount
for elem, count in other.items():
if elem not in self:
result[elem] = count
return result
counter1 = MyCounter({'a': 1, 'b': 0})
counter2 = MyCounter({'a': 2, 'c': 3})
print(counter1 + counter2) # MyCounter({'a': 3, 'c': 3, 'b': 0})
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I'll help Anand S Kumar
make more additional explanations.
Even if your dict contains a negative value, it still preserves your keys.
from collections import Counter
a = {"a": 1, "b": 5, "d": -1}
b = {"b": 1, "c": 2}
print Counter(a) + Counter(b)
#Counter({'b': 6, 'c': 2, 'a': 1})
x = Counter(a)
x.update(Counter(b))
print x
#Counter({'b': 6, 'c': 2, 'a': 1, 'd': -1})
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