Count number of similar items in list python

I am new to Python. I am trying to find a simple way of getting a count of the number of elements repeated in a list e.g.

MyList = ["a", "b", "a", "c", "c", "a", "c"]

Output:

a: 3
b: 1
c: 3

galoget

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asked Apr 23, 2014 at 10:00

0

You can do that using count:

my_dict = {i:MyList.count(i) for i in MyList}

>>> print my_dict     #or print(my_dict) in python-3.x
{'a': 3, 'c': 3, 'b': 1}

Or using collections.Counter:

from collections import Counter

a = dict(Counter(MyList))

>>> print a           #or print(a) in python-3.x
{'a': 3, 'c': 3, 'b': 1}

djvg

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answered Apr 23, 2014 at 10:01

sshashank124sshashank124

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10

Use Counter

>>> from collections import Counter
>>> MyList = ["a", "b", "a", "c", "c", "a", "c"]
>>> c = Counter(MyList)
>>> c
Counter({'a': 3, 'c': 3, 'b': 1})

answered Apr 23, 2014 at 10:08

Jayanth KoushikJayanth Koushik

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This works for Python 2.6.6

a = ["a", "b", "a"]
result = dict((i, a.count(i)) for i in a)
print result

prints

{'a': 2, 'b': 1}

answered Apr 23, 2014 at 10:19

Peter KellyPeter Kelly

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1

yourList = ["a", "b", "a", "c", "c", "a", "c"]

expected outputs {a: 3, b: 1,c:3}

duplicateFrequencies = {}
for i in set(yourList):
    duplicateFrequencies[i] = yourList.count(i)

Cheers!! Reference

answered Apr 23, 2014 at 10:06

Daniel AdenewDaniel Adenew

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1

In [2]: MyList = ["a", "b", "a", "c", "c", "a", "c"]

In [3]: count = {}

In [4]: for i in MyList:
   ...:     if not i in count:
   ...:         count[i] = 1
   ...:     else:
   ...:         count[i] +=1
   ...:

In [5]: count
Out[5]: {'a': 3, 'b': 1, 'c': 3}

answered Apr 23, 2014 at 10:08

If you want to count duplicates for a given element then use the count() function. Use a counter() function or basics logic combination to find all duplicated elements in a list and count them in Python.

Simple example code.

Using count()

Get the occurrence of a given element in the List. Count “b” in the list.

MyList = ["b", "a", "a", "c", "b", "a", "c", 'a']

res = MyList.count('b')

print(res)

Output: 2

And if want to count each of the elements in the List using for loop.

MyList = ["b", "a", "a", "c", "b", "a", "c", 'a']
res = {}

for i in MyList:
    res[i] = MyList.count(i)
    
print(res)

Output:

Same code using list comprehension

MyList = ["b", "a", "a", "c", "b", "a", "c", 'a']
res = {i:MyList.count(i) for i in MyList}

print(res)

Using collections.Counter()

You need to import Counter from the collection.

from collections import Counter

MyList = ["a", "b", "a", "c", "c", "a", "c"]
res = Counter(MyList)

print(res)
print(res['a'])

Output:

Counter({‘a’: 3, ‘c’: 3, ‘b’: 1})
3

Do comment if you have any doubts and suggestions on this Python list topic.

Note: IDE: PyCharm 2021.3.3 (Community Edition)

Windows 10

Python 3.10.1

All Python Examples are in Python 3, so Maybe its different from python 2 or upgraded versions.

Degree in Computer Science and Engineer: App Developer and has multiple Programming languages experience. Enthusiasm for technology & like learning technical.

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