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Python slice string

Published on August 3, 2022
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By Pankaj
Developer and author at DigitalOcean.
Python slice string

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Python string supports slicing to create substring. Note that Python string is immutable, slicing creates a new substring from the source string and original string remains unchanged.

Python slice string

Python slice string syntax is:

str_object[start_pos:end_pos:step]

The slicing starts with the start_pos index (included) and ends at end_pos index (excluded). The step parameter is used to specify the steps to take from start to end index. Python String slicing always follows this rule: s[:i] + s[i:] == s for any index ‘i’. All these parameters are optional - start_pos default value is 0, the end_pos default value is the length of string and step default value is 1. Let’s look at some simple examples of string slice function to create substring.

s = 'HelloWorld'

print(s[:])

print(s[::])

Output:

HelloWorld
HelloWorld

Note that since none of the slicing parameters were provided, the substring is equal to the original string. Let’s look at some more examples of slicing a string.

s = 'HelloWorld'
first_five_chars = s[:5]
print(first_five_chars)

third_to_fifth_chars = s[2:5]
print(third_to_fifth_chars)

Output:

Hello
llo

Note that index value starts from 0, so start_pos 2 refers to the third character in the string.

Reverse a String using Slicing

We can reverse a string using slicing by providing the step value as -1.

s = 'HelloWorld'
reverse_str = s[::-1]
print(reverse_str)

Output: dlroWolleH Let’s look at some other examples of using steps and negative index values.

s1 = s[2:8:2]
print(s1)

Output: loo Here the substring contains characters from indexes 2,4 and 6.

s1 = s[8:1:-1]
print(s1)

Output: lroWoll Here the index values are taken from end to start. The substring is made from indexes 1 to 7 from end to start. python slice string

s1 = s[8:1:-2]
print(s1)

Output: lool python slice string reverse Python slice works with negative indexes too, in that case, the start_pos is excluded and end_pos is included in the substring.

s1 = s[-4:-2]
print(s1)

Output: or python string slicing substring negative index Python string slicing handles out of range indexes gracefully.

>>>s = 'Python'
>>>s[100:]
''
>>>s[2:50]
'thon'

That’s all for python string slice function to create substring.

You can checkout complete python script and more Python examples from our GitHub Repository.


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About the authors
Default avatar
Pankaj

author

Developer and author at DigitalOcean.

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Was this helpful?

Plz tell me the slice of ‘HeloWr’

- Aadi

    TheData = [20, 3, 4,8,12, 99,4, 26 , 4 ] TheData1= TheData [ 0 : len(TheData) : 1 ] def InsertionData (TheData1): for Count in range(0, len(TheData1)): DataToInsert = TheData1(Count) Inserted = 0 Nextvalue = Count - 1 while (Nextvalue >= 0 and Inserted != 1): if DataToInsert < TheData1(Nextvalue): TheData1(Nextvalue + 1) == TheData1(Nextvalue) Nextvalue = Nextvalue -1 TheData1(Nextvalue +1 ) == DataToInsert else: Inserted = 1 def printarray(TheData1): for count in range(0, len(TheData1)): print(TheData1(count) ) print("Array before sorting \n ") printarray(TheData1) InsertionData(TheData1) print(“Array After sorting \n”) printarray(TheData1) Error: Array before sorting Traceback (most recent call last): File “c:\Users\Admin\Desktop\Paper 4 solution.py”, line 26, in printarray(TheData1) File “c:\Users\Admin\Desktop\Paper 4 solution.py”, line 23, in printarray print(TheData1(count) ) TypeError: ‘list’ object is not callable Anyone help how to done slicing in python

    - malik

      what does s(5:5) return

      - pradeep

        Your idea about reverse a string using a negative value is completely wrong please update this post. What actually happening here is x = ‘H e l l o w o r l d’ -----0 1 2 3 4 5 6 7 8 9 >>> x[8:1:-1] output – ‘ l r o w o l l ‘ -------8 7 6 5 4 3 2 Usually, the second parameter 1 won’t be taken into consideration right. This means if I enter x[1:8], index 8 won’t be sliced right. Similarly, this happens in x[8:1:-1]. So index 1 won’t be sliced. >>> x[-2:-8:-1] output- ‘lrowol’ Here, -2,-3,-4,-5,-6,-7 indexes will be sliced. Conclusion: string[x:y:p] When p x>y and index y won’t be sliced. That’ it!!!

        - Kobinarth Panchalingam

          please alter your article : the negative indexing is wrong

          - mostafa

            For the negative count, the end of the string starts from -1 not 0. It is like -4 -3 -2 -1 not -4 -3 -2 -1 0

            - Coder

              Hi I have a doubt: string = “Hi There” print (string[-4:-2]) and the output is ‘he’ but shouldn’t the output be ‘eh’? I am unable to understand why the output is showing he

              - Kalpit

                Can you explain the last one a little bit? s[-4:-2] Thanks!

                - Enoc

                  Hi Thankx for this section. I need more clarification on s1 = s[8:1:-1] print(s1) Output: lroWoll I am unable to get it .

                  - sradhanjali behera

                    thanks pankaj!!!

                    - curry lover 68