Python string number of occurrences

Find all occurrences of a substring in a string in Python

In this Python tutorial, we will learn how to find all occurrences of a substring in a string.

Table Of Contents

Find all occurrences of a substring using count()

The count() method is used to count the total occurrences of the given substring in a string. It takes three parameters.

string.count(substring,start,end)

Parameters
1. substring is the string to be counted
2. start is an optional parameter that takes an integer such that counting is started from the given index position.
3. end is an optional parameter that takes an integer such that counting is ended up to the given index position.

Frequently Asked:

It returns the number of occurrences of substring in from index positions start to end in the calling string object.

In this example, we will count the substring-“Python”.

# String string1="""Python programming language. Python is object-oriented, Python supports database connectivity and Python supports List,set, tuple and dictionary""" # Get the total number of occurrences - Python num = string1.count("Python") print(num)

We can see that “Python” occurred 4 times in the string.

In this example, we will count the substring-“Python” from a particular position.

# String string1="""Python programming language. Python is object-oriented, Python supports database connectivity and Python supports List,set, tuple and dictionary""" # Get the total number of occurrences - # Python from 1st position to 20th position num = string1.count("Python",0,19) print(num) # Get the total number of occurrences - # Python from 21st position to 65th position num = string1.count("Python",20,64) print(num)

We can see that “Python” occurred 1 time from the 1st position to the 20th position in the string and 2 times from the 21st position to the 65th position.

Find all occurrences of a substring using startswith()

The startswith() method is used to return the starting index of a particular substring. If we want to return all occurrence indices, we have to use list comprehension.

[iterator for iterator in range(len(string)) if string.startswith(substring, iterator)]

Parameters
1. substring is the string to be counted
2. iterator represents the position

To return the total number of occurrences, then we can apply the len() function to it.

len([iterator for iterator in range(len(string)) if string.startswith(substring, iterator)])

In this example, we will get the starting indices of the substring-“Python” and return the total number of occurrences.

# String string1="""Python programming language. Python is object-oriented, Python supports database connectivity and Python supports List,set, tuple and dictionary""" # Get the all indexpositions where substring "Python" exist in the string indices = [i for i in range(len(string1)) if string1.startswith("Python", i)] print(indices) # Get the total number of occurrences of "Python" num = len([i for i in range(len(string1)) if string1.startswith("Python", i)]) print(num)

We can see that “Python” occurred 4 times in the string and starting indices were also returned.

In this example, we will get the starting indices of the substring-“supports” and return the total number of occurrences.

# String string1="""Python programming language. Python is object-oriented, Python supports database connectivity and Python supports List,set, tuple and dictionary""" # Get the all indexpositions where substring "supports" exist in the string indices = [i for i in range(len(string1)) if string1.startswith("supports", i)] print(indices) # Get the total number of occurrences of "supports" num = len([i for i in range(len(string1)) if string1.startswith("supports", i)]) print(num)

We can see that “supports” occurred 2 times in the string and starting indices were also returned.

Find all occurrences of a substring using finditer()

The finditer() method is available in the re module which is used to return the starting index of a particular substring using the start() method. If we want to return all occurrence indices, we have to use list comprehension and iterate the string using an iterator.

[iterator.start() for iterator in re.finditer(substring, string)]

Parameters
1. substring is the string to be counted
2. string is the actual string

It returns a sequence a list of index positions where substring exists in the string. To return the total number of occurrences, then we can apply the len() function to it.

In this example, we will get the starting indices of the substring-“Python” and return the total number of occurrences.

import re # String string1="""Python programming language. Python is object-oriented, Python supports database connectivity and Python supports List,set, tuple and dictionary""" # Get the all indexpositions where substring "Python" exist in the string indices = [i.start() for i in re.finditer("Python", string1)] print(indices) # Get the total number of occurrences of "Python" num = len(indices) print(num)

We can see that “Python” occurred 4 times in the string and starting indices were also returned.

In this example, we will get the starting indices of the substring-“supports” and return the total number of occurrences.

import re # String string1="""Python programming language. Python is object-oriented, Python supports database connectivity and Python supports List,set, tuple and dictionary""" # Get the all indexpositions where substring "supports" exist in the string indices = [i.start() for i in re.finditer("supports", string1)] print(indices) # Get the total number of occurrences of "supports" num = len(indices) print(num)

We can see that “supports” occurred 2 times in the string and starting indices were also returned.

Summary

We have seen how to find and return the total number of occurrences of a particular substring using count(), startswith(), and finditer() methods. The startswith() and finditer() methods used list comprehension to return all the occurrences.

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Python Count Number of Occurrences Characters in a String

Count number of occurrences or substrings of a character in a string in python; This tutorial will demonstrate these things by writing a program to count the number of times occurrences character appears in a given string in python. And you will learn how to count occurrences of a character or substring in a string with examples.

How to count the number of occurrences of characters in a string in python

Use the python standard built-in string count() function to count a number of occurrences or substrings of a character in a string in python.

Before writing a Python program to count occurrences of a substring in a string, you must know about the python count() function:

Python String Count Function

Python string count() is a standard inbuilt function, which is used to find number of occurrences of the substring in the given string. The count() method searches the substring in the given string and returns how many times the substring is present in it.

It also takes optional parameters to start and end to specify the starting and ending positions in the string respectively.

Syntax of the python count functions is the following:

string.count(substring, start, end)

Here, the python count function accept three parameters and two parameters are optional.

substring is the first parameter of the python count function and is required parameter which is a string whose count is to be found.

The start parameter is an Optional which is the starting index within the string where the search starts.

The end parameter is an Optional which is the ending index within the string where the search ends.

Example 1: python count number of occurrences in the string

str = 'welcome to python words. Learn online python free.' substring = 'on' count = str.count(substring) print('The substring occurs <> times'.format(count))

In the above python program to count the number of characters in a string. i.e. on as a substring and check how many times it is repeated inside the Python String.

You can see the output of above python program to count the number of characters in a string:

The substring occurs 3 times

Example 2: python count function with start and end

str = 'welcome to python words. Learn online python free.' substring = 'on' count = str.count(substring, 10, 20) print('The substring occurs <> times'.format(count))

The above python program to count substring in the given string, we have used start and end parameters of python count function. It will count the number of substrings between the 10th and 20th index characters. In our example, on occurs only one time between those characters that is why we see the one time.

In the above python program to count the number of characters in a string. i.e. on as a substring and check how many times it is repeated inside the Python String.

You can see the output of the above python program to count the number of characters in a string:

The substring occurs 1 times

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Python String count()

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)

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)

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.

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