How to Substring a String in Python Complete Guide

Are you looking to find ways in Python how you can substring a string? Python 3.0 provides a lot of ways to do substring of strings. It in terms of python it’s called slicing.

To Perform or to make a substring of any given string you have to follow below template.

string[start: end: step:]

Here “start” is the starting index of the main string from which you want the substring to start. If in your code you skip start then it will automatically consider start as 0 i.e. starting index of the main string.

The “end” here represents the last index of the main string which will be the end index of your substring. By default, if the end is not included then It will be considered as the length of the main string.

The last “step” represents the number after each insertion you want to increase. By default, it is set to 1. Hence once it adds one character it moves to another one. Suppose after adding one character you want to skip next and add another one then you have to set step as 2.

For Example:

newString = "You are on Coduber.com"
print(newString[11:22:1])
##output = Coduber.com

print(newString[0:22:2])
#output = Yuaeo oue.o

Different Templates for Substring a String in Python

  • string[start : end] : Slice the string in a substring from a starting index “start” to the “end”-1.
  • string[: end] : Slice the string in a substring from beginning to “end”-1.
  • string[start: ] Slice the string in a substring from a starting index “start” until the string’s end.

Please note: the “start” index can be positive as well as negative. A Negative Start index means that you want to start the substring index to start from the end of the string minus the index provided instead of simply from starting of the index plus. Similarly, A Negative End index means that you want to end the substring from the beginning of the string till the end of the string minus the index. Below are the examples for all the negative indexes as well with output.

Further Examples of Above Templates

newString = "You are on Coduber.com"

#get the string between starting character 11 till the character 22-1.
print(newString[11:22])
##output = Coduber.com

#get First 4 Character of a string
print(newString[:4])
#output = You

#get last 11 character of a string
print(newString[11:])
#output =  Coduber.com

#get the starting substring of a string except the last 4 character.
print(newString[:-4])
#output = You are on Coduber

#get the substring as last 3 character of a string.
print(newString[-3:])
#outpu = com

#more example of negative index.
print(newString[-11:-4])
#output =  Coduber.com

Note that print(newString[:4]) is similar to print(newString[0:4]). Similarly print(newString[11:]) is same as print(newString[11:22]) as the length of the string is 22 here.

How to Substring a String in Python Complete Guide

Validate or Check if a substring is present within another string in Python

You can check any substring whether it’s part of a larger string or not very quickly and easily in python by using the “in” operator. Below is the template of the code you can use for example.

substring in string

Let us take a example with a working code.

newString = "You are on Coduber.com"
subString = "Coduber"
otherString = "guide"

print(subString in newString)
#Output = True

print(otherString in newString)
#output = False

The “in” operator return True or False based upon the comparison whether the substring is present in the string or not. But if you want the starting index of the substring present in the string then you have to use find function in Python. Its a inbuilt function which returns starting index of the substring in the string. If the substring is not found in the string then -1 is returned.

Let check an example to get the starting index of the substring in the string.

newString = "You are on Coduber.com"
subString = "Coduber"
otherString = "guide"

print(newString.find(subString))
#Output = 11

print(newString.find(otherString))
#Output = -1

You should learn to run the python script as well if you do not know and want to learn.

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