Python find all spaces in string

Find All Substrings of String in Python

Dealing with and manipulating strings is a fundamental part of understanding the basics of Python, and the use of substrings and strings can be seen in essentially every Python program. This tutorial focuses on one such part of substrings. The article demonstrates the different approaches available to find all substrings of string in Python.

what Is a String in Python?

A string is a collection or a sequence of characters stored in a variable, and is usually enclosed within single quotes or double-quotes. It is one of the most versatile data types in Python, as it is capable of storing anything, whether it is a character or a number.

what Is a Substring?

A substring can be defined as any sequence of characters that are contained within a string. In simple terms, it can be said to be a slice or a small part of the original string.

How To Find All Substrings of String in Python?

There are mainly three methods to implement the task at hand, with all of these approaches being drastically dissimilar to one another.

Using a User-Defined Function that Makes Use of String Slicing to Find All Substrings of String in Python.

We can simply create a user-defined function that makes use of string slicing to implement the task of finding all substrings of string in Python.

List slicing is a general practice that is widely utilized while dealing with lists in Python, as it provides users the ability to manipulate strings efficiently.

With list slicing, we can emphasize the portion of the string that we would want to get, and it specifically returns that part or portion of the list. Based on this, there is another term known as string slicing, which implements the same idea on a string, which is what we will implement by using this approach.

The following code uses a user-defined function that makes use of string slicing to find all substrings of string in Python.

The above code provides the following output:

[‘j’, ‘ja’, ‘jav’, ‘java’, ‘java2’, ‘java2b’, ‘java2bl’, ‘java2blo’, ‘java2blog’, ‘a’, ‘av’, ‘ava’, ‘ava2’, ‘ava2b’, ‘ava2bl’, ‘ava2blo’, ‘ava2blog’, ‘v’, ‘va’, ‘va2’, ‘va2b’, ‘va2bl’, ‘va2blo’, ‘va2blog’, ‘a’, ‘a2’, ‘a2b’, ‘a2bl’, ‘a2blo’, ‘a2blog’, ‘2’, ‘2b’, ‘2bl’, ‘2blo’, ‘2blog’, ‘b’, ‘bl’, ‘blo’, ‘blog’, ‘l’, ‘lo’, ‘log’, ‘o’, ‘og’, ‘g’]

Using List Comprehension Along with String Slicing to Find All Substrings of String in Python.

The same approach mentioned above can be utilized along with using list comprehension in Python.

List comprehension provides a compact way of creating a list when values are to be taken from an already existing list. The list comprehension code is generally a one-liner and provides conciseness to the Python code. Moreover, it also eliminates the need to manually utilize the for loop across multiple lines to define the process of creating another list.

Apart from making the code smaller, it also decreases the compile time of the code, which makes it a useful asset when writing large complex codes.

The following code uses list comprehension along with string slicing to find all substrings of string in Python.

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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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