10 examples of using string methods in python

by Alex
10 examples of using string methods in python
A string is a sequence of characters. The built-in string class in Python is strings based on the Unicode character set, the international character encoding standard. Strings work with basic Python operations and some additional exclusive methods.

In this material, let’s explore the most used ones. It is important to note here that all string methods always return new values, not change the original string.

1. Aligning a string to the center

The center() method aligns a string to the center. The alignment is performed at the expense of a certain character (by default, it’s a space). The syntax is str.center(length, fillchar), where:

  • length – the length of the string (mandatory);
  • fillchar – the character that defines the alignment (optional);

Example code

sentence = 'algorithm'
sentence.center(14,'-')
'---algorithm---'

2. How many times the character occurs in the string

The count() method returns how many times a particular value occurs in the string. The syntax is str.count(value, start, end), where:

  • value – substring which should be searched in the string (obligatory);
  • start – start index of the string, where the search should start (optional);
  • end – the end index of the string, where the search for the value should end (optional);

Example code

sentence = 'She sells seashells by the sea. The goods she sells are certainly seashells.'
sentence.count('shells')
sentence.count('seashells',9,25)
2
1

3. Search for a substring in a string

The find() method returns the smallest index of the position where the specified substring occurs in the string. If it is not found, it returns -1.

Syntax str.find(value, start, end), where:

  • value – substring to be searched in the string (mandatory);
  • start – the start index of the string, where the search should start from (optional);
  • end – the end index of the string, where the search for the value should end (optional);

Types

  • rfind() – The rfind() method is similar to find(), but it returns the largest index.

Example code

sentence = 'She sells seashells by the sea. The goods she sells are definitely seashells.'
sentence.find('shells')
sentence.find('shells',0,9)
sentence.find('p',5,10)
sentence.rfind('shells')
10
-1
8
69

4. Mirroring the case of a string

The swapcase() method returns a copy of the string, where all letters in lower case are written in upper case and vice versa.

Syntax string.swapcase() Example code

sentence = 'Queue is another FUNDAMENTAL data structure'
sentence.swapcase()
'qUEUE IS ONE MORE FUNDAMENTAL DATA STRUCTURE'

5. Search at the beginning or at the end of string

The startswith() method returns True if the string starts with the given value; otherwise it returns False. The endswith() method returns False if the string ends with a particular value; otherwise – False. Syntax string.startswith(value, start, end) string.endsswith(value, start, end)

  • value is the value to look for in the string (mandatory);
  • start is the start index of the string where you want to start the search (optional);
  • end – the end index of the string, where the search for the value should end (optional);

Example code

#string.startswith()

sentence = 'Binary search - the classic recursive algorithm'
sentence.startswith("Binary")
sentence.startswith("search",7,20)
True
True
#string.endswith()
sentence.endswith('classic')
False

6. Turning a string into a list

The split() method returns a list of string words, with space as the default delimiter. Syntax string.split(sep, maxsplit)

  • sep is a separator used to separate strings. If nothing is specified, it is a space (optional);
  • maxsplit() – indicates the number of separations. The default value (-1) means “in all cases” (optional);

Types

  • rsplit() – splits the string starting from the right side.

Example code

#string.split()

fruits = 'apples, mangoes, bananas, grapes'
fruits.split()
fruits.split(",",maxsplit = 2)
['apples,', 'mangoes,', 'bananas,', 'grapes']
['apples', 'mangoes', 'bananas, grapes']
#string.rsplit()
fruits.rsplit(",",maxsplit = 1)
['apples, mangoes, bananas', ' grapes']

7. Changing the case of a string

7.1. first character to uppercase

The capitalize() method capitalizes only the first character of the string. Syntax string.capitalize()

'san francisco'.capitalize()
'san francisco'

7.2. upper case all characters

The method upper() makes all characters of the string upper case. The syntax is string.upper()

"san francisco".upper()
'SAN FRANCISCO'

7.all first letters of the words to upper case

The title() method capitalizes all the first letters in words of a given string. Syntax string.title()

"san francisco."title()
'San Francisco'

8. Left or right alignment of lines

The ljust() method returns a left-aligned string with a specified character (space by default). The rjust() method aligns the string to the right edge. Syntax string.rjust/ljust(length, character)

  • length – length of the string to be returned (mandatory);
  • character – character used to fill the empty space, space by default (optional);

Example code

#str.rjust
text = 'Binary search - '
print(text.rjust(25),'classical recursive algorithm')
        Binary search - the classical recursive algorithm
#str.ljust
text = 'Binary search - '
print(text.ljust(25),'classical recursive algorithm')
Binary search - the classical recursive algorithm

9. Removing spaces around a string

The strip() method returns a copy of the string with certain characters at the beginning and end of the string removed. Space is the default character. The syntax is string.strip(character) Types

  • rstrip() – removes characters from the right side of the string.
  • lstrip() – removes characters from the left side of the string.

Example

#str.strip
string = '#.......Section 3.2.1 Question #32......'
string.strip('.#!')
'Section 3.2.1 Question #32'
#str.rstrip
string.rstrip('.#!')
string.lstrip('.#!')
'#.......Section 3.2.1 Question #32'
'Section 3.2.1 Question #32......'

10. Adding zeros at the beginning of a line

The zfill() method adds zeros (0) at the beginning of the string. The length of the returned string depends on the specified width. Syntax string.zfill(width)

  • the width determines the length of the string to be returned. Zeros are not added if the width parameter is less than the length of the original string.

Example

'7'.zfill(3)
'-21'.zfill(5)
'Python'.zfill(10)
'Python'.zfill(3)
'007'
'-0021'
'0000Python'
'Python'

Outputs

These are just some of the useful string methods built into Python. There are others that are just as important. The article Strings in python 3: Methods, Functions, Formatting is a great resource for delving into all the details.

Related Posts

LEAVE A COMMENT