Understand Python String startswith() Function for Python Beginner – Python Tutorial

By | July 20, 2019
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Like python string endswith() function, in this tutorial, we will introduce how to use python string startswith() function. This function is very useful to help us to filter string.

python startswith function

  1. str.startswith(prefix[, start[, end]])
str.startswith(prefix[, start[, end]])

Parameters

prefix – String or tuple of strings to be checked
start (optional) – Beginning position where prefix is to be checked within the string.
end (optional) – Ending position where prefix is to be checked within the string.

Return Value

True or False

Here are some useful example.

suffix is a string

  1. suffix = 'https'
  2. str = 'https://www.tutorialexample.com'
  4. starts = str.startswith(suffix)
  5. print(starts)
  6. #True
suffix = 'https'
str = 'https://www.tutorialexample.com'

starts = str.startswith(suffix)
print(starts)
#True

startswith() is case sensitive?

  1. suffix = 'HTTPS'
  2. str = 'https://www.tutorialexample.com'
  4. starts = str.startswith(suffix)
  5. print(starts)
  6. #False
suffix = 'HTTPS'
str = 'https://www.tutorialexample.com'

starts = str.startswith(suffix)
print(starts)
#False

From the result, we can find string startswith() function is case sensitive.

If start > len(str)?

  1. starts = str.startswith(suffix, len(str))
  2. print(starts)
  3. #False
starts = str.startswith(suffix, len(str))
print(starts)
#False

suffix is a tuple

  1. suffix = ('https', 'https://')
  2. str = 'https://www.tutorialexample.com'
  4. starts = str.startswith(suffix) #1
  5. print(starts)
  6. #True
  7. pass
  9. suffix = ('https', 'ftp://')
  10. starts = str.startswith(suffix) #2
  11. print(starts)
  12. #True
  14. suffix = ('ftp', 'ftp://')
  15. starts = str.startswith(suffix) #3
  16. print(starts)
  17. #False
suffix = ('https', 'https://')
str = 'https://www.tutorialexample.com'

starts = str.startswith(suffix) #1
print(starts)
#True
pass

suffix = ('https', 'ftp://') 
starts = str.startswith(suffix) #2
print(starts)
#True

suffix = ('ftp', 'ftp://')
starts = str.startswith(suffix) #3
print(starts)
#False

From the result, we will find these truth when suffix is a tuple.

  • String starts with any element in suffix will return True (#1 and #2).
  • Only String starts with none of elements in suffix will return False (#3).

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