Count elements in string python

In this tutorial, we will learn about the Python String count() method with the help of examples.

The count() method returns the number of occurrences of a substring in the given string.

Example

message = 'python is popular programming language'

# number of occurrence of 'p' print('Number of occurrence of p:', message.count('p'))

# Output: Number of occurrence of p: 4


Syntax of String count

The syntax of count() method is:

string.count(substring, start=..., end=...)

count() Parameters

count() method only requires a single parameter for execution. However, it also has two optional parameters:

  • substring - string whose count is to be found.
  • start (Optional) - starting index within the string where search starts.
  • end (Optional) - ending index within the string where search ends.

Note: Index in Python starts from 0, not 1.


count() Return Value

count() method returns the number of occurrences of the substring in the given string.


Example 1: Count number of occurrences of a given substring

# define string
string = "Python is awesome, isn't it?"
substring = "is"

count = string.count(substring)

# print count print("The count is:", count)

Output

The count is: 2

Example 2: Count number of occurrences of a given substring using start and end

# define string
string = "Python is awesome, isn't it?"
substring = "i"

# count after first 'i' and before the last 'i'

count = string.count(substring, 8, 25)

# print count print("The count is:", count)

Output

The count is: 1

Here, the counting starts after the first i has been encountered, i.e. 7th index position.

And, it ends before the last i, i.e. 25th index position.

How do I count the number of occurrences of a character in a string?

e.g. 'a' appears in 'Mary had a little lamb' 4 times.

Count elements in string python

Mateen Ulhaq

22.2k16 gold badges86 silver badges127 bronze badges

asked Jul 20, 2009 at 20:00

2

str.count(sub[, start[, end]])

Return the number of non-overlapping occurrences of substring sub in the range [start, end]. Optional arguments start and end are interpreted as in slice notation.

>>> sentence = 'Mary had a little lamb'
>>> sentence.count('a')
4

Count elements in string python

Mateen Ulhaq

22.2k16 gold badges86 silver badges127 bronze badges

answered Jul 20, 2009 at 20:04

Ogre CodesOgre Codes

17.7k1 gold badge16 silver badges24 bronze badges

2

You can use .count() :

>>> 'Mary had a little lamb'.count('a')
4

Count elements in string python

Mateen Ulhaq

22.2k16 gold badges86 silver badges127 bronze badges

answered Jul 20, 2009 at 20:04

eduffyeduffy

38.2k12 gold badges93 silver badges91 bronze badges

To get the counts of all letters, use collections.Counter:

>>> from collections import Counter
>>> counter = Counter("Mary had a little lamb")
>>> counter['a']
4

Count elements in string python

Mateen Ulhaq

22.2k16 gold badges86 silver badges127 bronze badges

answered Aug 1, 2012 at 22:12

Brenden BrownBrenden Brown

3,0551 gold badge13 silver badges15 bronze badges

4

Regular expressions maybe?

import re
my_string = "Mary had a little lamb"
len(re.findall("a", my_string))

answered Jul 20, 2009 at 20:03

Sinan TaifourSinan Taifour

10.1k3 gold badges31 silver badges30 bronze badges

6

Python-3.x:

"aabc".count("a")

str.count(sub[, start[, end]])

Return the number of non-overlapping occurrences of substring sub in the range [start, end]. Optional arguments start and end are interpreted as in slice notation.

Count elements in string python

tremendows

4,1943 gold badges31 silver badges51 bronze badges

answered Jul 20, 2009 at 20:05

Aaron FiAaron Fi

9,94613 gold badges64 silver badges91 bronze badges

1

myString.count('a');

more info here

answered Jul 20, 2009 at 20:04

Finer ReclinerFiner Recliner

1,5591 gold badge13 silver badges21 bronze badges

str.count(a) is the best solution to count a single character in a string. But if you need to count more characters you would have to read the whole string as many times as characters you want to count.

A better approach for this job would be:

from collections import defaultdict

text = 'Mary had a little lamb'
chars = defaultdict(int)

for char in text:
    chars[char] += 1

So you'll have a dict that returns the number of occurrences of every letter in the string and 0 if it isn't present.

>>>chars['a']
4
>>>chars['x']
0

For a case insensitive counter you could override the mutator and accessor methods by subclassing defaultdict (base class' ones are read-only):

class CICounter(defaultdict):
    def __getitem__(self, k):
        return super().__getitem__(k.lower())

    def __setitem__(self, k, v):
        super().__setitem__(k.lower(), v)


chars = CICounter(int)

for char in text:
    chars[char] += 1

>>>chars['a']
4
>>>chars['M']
2
>>>chars['x']
0

answered Oct 2, 2016 at 2:33

Count elements in string python

Nuno AndréNuno André

3,8301 gold badge29 silver badges40 bronze badges

3

This easy and straight forward function might help:

def check_freq(x):
    freq = {}
    for c in set(x):
       freq[c] = x.count(c)
    return freq

check_freq("abbabcbdbabdbdbabababcbcbab")
{'a': 7, 'b': 14, 'c': 3, 'd': 3}

If a comprehension is desired:

def check_freq(x):
    return {c: x.count(c) for c in set(x)}

rayryeng

101k21 gold badges181 silver badges185 bronze badges

answered Mar 20, 2018 at 13:19

Count elements in string python

0

Regular expressions are very useful if you want case-insensitivity (and of course all the power of regex).

my_string = "Mary had a little lamb"
# simplest solution, using count, is case-sensitive
my_string.count("m")   # yields 1
import re
# case-sensitive with regex
len(re.findall("m", my_string))
# three ways to get case insensitivity - all yield 2
len(re.findall("(?i)m", my_string))
len(re.findall("m|M", my_string))
len(re.findall(re.compile("m",re.IGNORECASE), my_string))

Be aware that the regex version takes on the order of ten times as long to run, which will likely be an issue only if my_string is tremendously long, or the code is inside a deep loop.

answered Dec 5, 2014 at 17:04

Count elements in string python

jafeldsjafelds

8648 silver badges12 bronze badges

1

I don't know about 'simplest' but simple comprehension could do:

>>> my_string = "Mary had a little lamb"
>>> sum(char == 'a' for char in my_string)
4

Taking advantage of built-in sum, generator comprehension and fact that bool is subclass of integer: how may times character is equal to 'a'.

answered Sep 20, 2020 at 8:55

Aivar PaalbergAivar Paalberg

4,1484 gold badges16 silver badges16 bronze badges

a = 'have a nice day'
symbol = 'abcdefghijklmnopqrstuvwxyz'
for key in symbol:
    print(key, a.count(key))

Count elements in string python

answered Oct 24, 2015 at 22:36

rookierookie

611 silver badge1 bronze badge

0

I am a fan of the pandas library, in particular the value_counts() method. You could use it to count the occurrence of each character in your string:

>>> import pandas as pd
>>> phrase = "I love the pandas library and its `value_counts()` method"
>>> pd.Series(list(phrase)).value_counts()
     8
a    5
e    4
t    4
o    3
n    3
s    3
d    3
l    3
u    2
i    2
r    2
v    2
`    2
h    2
p    1
b    1
I    1
m    1
(    1
y    1
_    1
)    1
c    1
dtype: int64

answered Jan 19, 2020 at 9:23

Count elements in string python

1

count is definitely the most concise and efficient way of counting the occurrence of a character in a string but I tried to come up with a solution using lambda, something like this :

sentence = 'Mary had a little lamb'
sum(map(lambda x : 1 if 'a' in x else 0, sentence))

This will result in :

4

Also, there is one more advantage to this is if the sentence is a list of sub-strings containing same characters as above, then also this gives the correct result because of the use of in. Have a look :

sentence = ['M', 'ar', 'y', 'had', 'a', 'little', 'l', 'am', 'b']
sum(map(lambda x : 1 if 'a' in x else 0, sentence))

This also results in :

4

But Of-course this will work only when checking occurrence of single character such as 'a' in this particular case.

answered Mar 28, 2017 at 17:13

Count elements in string python

An alternative way to get all the character counts without using Counter(), count and regex

counts_dict = {}
for c in list(sentence):
  if c not in counts_dict:
    counts_dict[c] = 0
  counts_dict[c] += 1

for key, value in counts_dict.items():
    print(key, value)

answered Mar 7, 2019 at 9:04

a = "I walked today,"
c=['d','e','f']
count=0
for i in a:
    if str(i) in c:
        count+=1

print(count)

answered Sep 29, 2020 at 3:27

KquekKquek

574 bronze badges

2

I know the ask is to count a particular letter. I am writing here generic code without using any method.

sentence1 =" Mary had a little lamb"
count = {}
for i in sentence1:
    if i in count:
        count[i.lower()] = count[i.lower()] + 1
    else:
        count[i.lower()] = 1
print(count)

output

{' ': 5, 'm': 2, 'a': 4, 'r': 1, 'y': 1, 'h': 1, 'd': 1, 'l': 3, 'i': 1, 't': 2, 'e': 1, 'b': 1}

Now if you want any particular letter frequency, you can print like below.

print(count['m'])
2

answered Feb 3, 2021 at 11:42

Rishi BansalRishi Bansal

3,4352 gold badges24 silver badges44 bronze badges

To find the occurrence of characters in a sentence you may use the below code

Firstly, I have taken out the unique characters from the sentence and then I counted the occurrence of each character in the sentence these includes the occurrence of blank space too.

ab = set("Mary had a little lamb")

test_str = "Mary had a little lamb"

for i in ab:
  counter = test_str.count(i)
  if i == ' ':
    i = 'Space'
  print(counter, i)

Output of the above code is below.

1 : r ,
1 : h ,
1 : e ,
1 : M ,
4 : a ,
1 : b ,
1 : d ,
2 : t ,
3 : l ,
1 : i ,
4 : Space ,
1 : y ,
1 : m ,

answered Sep 23, 2021 at 5:06

Count elements in string python

5

"Without using count to find you want character in string" method.

import re

def count(s, ch):

   pass

def main():

   s = raw_input ("Enter strings what you like, for example, 'welcome': ")  

   ch = raw_input ("Enter you want count characters, but best result to find one character: " )

   print ( len (re.findall ( ch, s ) ) )

main()

Count elements in string python

answered Jan 11, 2015 at 17:24

B-YB-Y

1671 gold badge2 silver badges12 bronze badges

1

Python 3

Ther are two ways to achieve this:

1) With built-in function count()

sentence = 'Mary had a little lamb'
print(sentence.count('a'))`

2) Without using a function

sentence = 'Mary had a little lamb'    
count = 0

for i in sentence:
    if i == "a":
        count = count + 1

print(count)

answered Sep 7, 2019 at 20:16

Dipen GajjarDipen Gajjar

1,17813 silver badges22 bronze badges

the easiest way is to code in one line:

'Mary had a little lamb'.count("a")

but if you want can use this too:

sentence ='Mary had a little lamb'
   count=0;
    for letter in sentence :
        if letter=="a":
            count+=1
    print (count)

answered Dec 21, 2021 at 13:34

3

str = "count a character occurence"

List = list(str)
print (List)
Uniq = set(List)
print (Uniq)

for key in Uniq:
    print (key, str.count(key))

Count elements in string python

answered Apr 1, 2016 at 1:29

Count elements in string python

1

Taking up a comment of this user:

import numpy as np
sample = 'samplestring'
np.unique(list(sample), return_counts=True)

Out:

(array(['a', 'e', 'g', 'i', 'l', 'm', 'n', 'p', 'r', 's', 't'], dtype='<U1'),
 array([1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 1]))

Check 's'. You can filter this tuple of two arrays as follows:

a[1][a[0]=='s']

Side-note: It works like Counter() of the collections package, just in numpy, which you often import anyway. You could as well count the unique words in a list of words instead.

answered Dec 29, 2021 at 19:29

Count elements in string python

No more than this IMHO - you can add the upper or lower methods

def count_letter_in_str(string,letter):
    return string.count(letter)

answered Feb 23, 2016 at 19:16

Count elements in string python

Tim SeedTim Seed

4,8762 gold badges27 silver badges26 bronze badges

You can use loop and dictionary.

def count_letter(text):
    result = {}
    for letter in text:
        if letter not in result:
            result[letter] = 0
        result[letter] += 1
    return result

Count elements in string python

blackbishop

28.6k10 gold badges53 silver badges70 bronze badges

answered Dec 24, 2021 at 10:03

Count elements in string python

spam = 'have a nice day'
var = 'd'


def count(spam, var):
    found = 0
    for key in spam:
        if key == var:
            found += 1
    return found
count(spam, var)
print 'count %s is: %s ' %(var, count(spam, var))

poolie

9,0421 gold badge46 silver badges73 bronze badges

answered Nov 15, 2015 at 19:05

How do you count items in a string?

The count() method returns the number of occurrences of a substring in the given string..
substring - string whose count is to be found..
start (Optional) - starting index within the string where search starts..
end (Optional) - ending index within the string where search ends..

How do you count occurrences of a character in a string?

First, we split the string by spaces in a. Then, take a variable count = 0 and in every true condition we increment the count by 1. Now run a loop at 0 to length of string and check if our string is equal to the word.

How do you count elements in a list Python?

The most straightforward way to get the number of elements in a list is to use the Python built-in function len() . As the name function suggests, len() returns the length of the list, regardless of the types of elements in it.

How do you count multiple strings in Python?

Python String count() function is an inbuilt function in python programming language that returns the number of occurrences of a substring in the given string..
Syntax:.
Parameters:.
Return Value:.

Tải thêm tài liệu liên quan đến bài viết Count elements in string python