StringPy.md

Strings Functions Explained - TheTestingAcademy

Python strings come with a variety of built-in methods that allow you to perform different operations on them. Here's a list of all common string methods available in Python, along with examples for each. This list is not exhaustive but covers the most frequently used methods.

1. capitalize()

• Description: Converts the first character of the string to uppercase.
• Example:

s = 'hello world'
print(s.capitalize())  # Output: 'Hello world'

2. casefold()

• Description: Converts string to lowercase, designed for caseless matching.
• Example:

s = 'HELLO World'
print(s.casefold())  # Output: 'hello world'

3. center(width, fillchar)

• Description: Returns a centered string of length width.
• Example:

s = 'hello'
print(s.center(20, '*'))  # Output: '*******hello********'

4. count(substring, start, end)

• Description: Returns the number of occurrences of a substring in the string.
• Example:

s = 'hello world'
print(s.count('o'))  # Output: 2

5. encode(encoding="utf-8", errors="strict")

• Description: Returns an encoded version of the string as a bytes object.
• Example:

s = 'hello world'
print(s.encode())  # Output: b'hello world'

6. endswith(suffix, start, end)

• Description: Returns True if the string ends with the specified suffix.
• Example:

s = 'hello world'
print(s.endswith('world'))  # Output: True

7. expandtabs(tabsize=8)

• Description: Replaces tabs in a string with the specified number of spaces.
• Example:

s = 'hello\tworld'
print(s.expandtabs(4))  # Output: 'hello   world'

8. find(sub, start, end)

• Description: Returns the lowest index in the string where substring sub is found.
• Example:

s = 'hello world'
print(s.find('world'))  # Output: 6

9. format(*args, **kwargs)

• Description: Formats the string using format specifiers.
• Example:

s = 'Hello, {}'
print(s.format('world'))  # Output: 'Hello, world'

10. format_map(mapping)

• Description: Formats the string using a dictionary.
• Example:

s = 'Hello, {name}'
print(s.format_map({'name': 'world'}))  # Output: 'Hello, world'

11. index(sub, start, end)

• Description: Like find(), but raises ValueError when the substring is not found.
• Example:

s = 'hello world'
print(s.index('world'))  # Output: 6

12. isalnum()

• Description: Returns True if all characters in the string are alphanumeric.
• Example:

s = 'hello123'
print(s.isalnum())  # Output: True

13. isalpha()

• Description: Returns True if all characters in the string are alphabetic.
• Example:

s = 'hello'
print(s.isalpha())  # Output: True

14. isdecimal()

• Description: Returns True if all characters in the string are decimal characters.
• Example:

s = '123'
print(s.isdecimal())  # Output: True

15. isdigit()

• Description: Returns True if all characters in the string are digits.
• Example:

s = '123'
print(s.isdigit())  # Output: True

16. isidentifier()

• Description: Returns True if the string is a valid identifier according to Python syntax.
• Example:

s = 'hello_world'
print(s.isidentifier())  # Output: True

17. islower()

• Description: Returns True if all cased characters in the string are lowercase.
• Example:

s = 'hello world'
print(s.islower())  # Output: True

18. isnumeric()

• Description: Returns True if all characters in the string are numeric characters.
• Example:

s = '123'
print(s.isnumeric())  # Output: True

19. isprintable()

• Description:

Returns True if all characters in the string are printable or the string is empty.

• Example:

s = 'hello world'
print(s.isprintable())  # Output: True

20. isspace()

• Description: Returns True if all characters in the string are whitespace.
• Example:

s = '   '
print(s.isspace())  # Output: True

21. istitle()

• Description: Returns True if the string is a title-cased string.
• Example:

s = 'Hello World'
print(s.istitle())  # Output: True

22. isupper()

• Description: Returns True if all cased characters in the string are uppercase.
• Example:

s = 'HELLO WORLD'
print(s.isupper())  # Output: True

23. join(iterable)

• Description: Joins the elements of an iterable to the string.
• Example:

s = '-'
print(s.join(['hello', 'world']))  # Output: 'hello-world'

24. ljust(width, fillchar)

• Description: Returns a left-justified string of length width.
• Example:

s = 'hello'
print(s.ljust(10, '*'))  # Output: 'hello*****'

25. lower()

• Description: Converts all characters in the string to lowercase.
• Example:

s = 'HELLO WORLD'
print(s.lower())  # Output: 'hello world'

26. lstrip(chars)

• Description: Returns a copy of the string with leading characters removed.
• Example:

s = '   hello world'
print(s.lstrip())  # Output: 'hello world'

27. partition(sep)

• Description: Splits the string at the first occurrence of sep.
• Example:

s = 'hello world'
print(s.partition(' '))  # Output: ('hello', ' ', 'world')

28. replace(old, new, count)

• Description: Returns a string where all occurrences of old have been replaced by new.
• Example:

s = 'hello world'
print(s.replace('world', 'Python'))  # Output: 'hello Python'

29. rfind(sub, start, end)

• Description: Returns the highest index in the string where substring sub is found.
• Example:

s = 'hello world, hello Python'
print(s.rfind('hello'))  # Output: 13

30. rindex(sub, start, end)

• Description: Like rfind(), but raises ValueError when the substring is not found.
• Example:

s = 'hello world, hello Python'
print(s.rindex('hello'))  # Output: 13

31. rjust(width, fillchar)

• Description: Returns a right-justified string of length width.
• Example:

s = 'hello'
print(s.rjust(10, '*'))  # Output: '*****hello'

32. rpartition(sep)

• Description: Splits the string at the last occurrence of sep.
• Example:

s = 'hello world, hello Python'
print(s.rpartition(' '))  # Output: ('hello world, hello', ' ', 'Python')

33. rsplit(sep=None, maxsplit=-1)

• Description: Splits the string at the separator sep and returns a list of strings.
• Example:

s = 'hello world hello Python'
print(s.rsplit(' ', 1))  # Output: ['hello world hello', 'Python']

34. rstrip(chars)

• Description: Returns a copy of the string with trailing characters removed.
• Example:

s = 'hello world   '
print(s.rstrip())  # Output: 'hello world'

35. split(sep=None, maxsplit=-1)

• Description: Splits the string at the separator sep and returns a list.
• Example:

s = 'hello world hello Python'
print(s.split())  # Output: ['hello', 'world', 'hello', 'Python']

36. splitlines(keepends=False)

• Description: Splits the string at line breaks and returns a list of lines.
• Example:

s = 'hello\nworld'
print(s.splitlines())  # Output: ['hello

', 'world']

37. startswith(prefix, start, end)

• Description: Returns True if the string starts with the specified prefix.
• Example:

s = 'hello world'
print(s.startswith('hello'))  # Output: True

38. strip(chars)

• Description: Returns a copy of the string with leading and trailing characters removed.
• Example:

s = '   hello world   '
print(s.strip())  # Output: 'hello world'

39. swapcase()

• Description: Converts uppercase characters to lowercase and vice versa.
• Example:

s = 'Hello World'
print(s.swapcase())  # Output: 'hELLO wORLD'

40. title()

• Description: Returns a title-cased version of the string.
• Example:

s = 'hello world'
print(s.title())  # Output: 'Hello World'

41. translate(table)

• Description: Returns a copy of the string in which each character has been mapped through a given translation table.
• Example:

# Translation table to replace 'h' with 'j'
trans = str.maketrans('h', 'j')
s = 'hello world'
print(s.translate(trans))  # Output: 'jello world'

42. upper()

• Description: Converts all characters in the string to uppercase.
• Example:

s = 'hello world'
print(s.upper())  # Output: 'HELLO WORLD'

43. zfill(width)

• Description: Pads the string on the left with zeros to fill width.
• Example:

s = '42'
print(s.zfill(5))  # Output: '00042'

These methods are part of the core Python language and provide powerful tools for manipulating strings in various ways.