5.4. String Methods
str.upper()- all letters will be uppercasestr.lower()- all letters will be lowercasestr.capitalize()- will uppercase first letter of text, lowercase othersstr.title()- will uppercase first letter of each word, lowercase othersstr.swapcase()- make lowercase letters upper, and uppercase lowerstr.casefold()- Return a version of the string suitable for caseless comparisons
5.4.1. Upper
str.upper()- all letters will be uppercase
>>> name = 'Angus MacGyver III'
>>>
>>> name.upper()
'ANGUS MACGYVER III'
5.4.2. Lower
str.lower()- all letters will be lowercase
>>> name = 'Angus MacGyver III'
>>>
>>> name.lower()
'angus macgyver iii'
5.4.3. Capitalize
str.capitalize()- will uppercase first letter of text, lowercase others
>>> name = 'Angus MacGyver III'
>>>
>>> name.title()
'Angus Macgyver Iii'
5.4.4. Title
str.title()- will uppercase first letter of each word, lowercase others
>>> name = 'Angus MacGyver III'
>>>
>>> name.capitalize()
'Angus macgyver iii'
5.4.5. Swapcase
str.swapcase()- make lowercase letters upper, and uppercase lower
>>> name = 'Angus MacGyver III'
>>>
>>> name.swapcase()
'aNGUS mACgYVER iii'
5.4.6. Casefold
str.casefold()- Return a version of the string suitable for caseless comparisons
str.casefold() is a more aggressive method for converting strings to lowercase
than str.lower(). It is designed for caseless matching, especially for Unicode
text, and can handle more language-specific cases (e.g., German "ß" becomes "ss"
with str.casefold(), but remains "ß" with str.lower()). Use str.casefold()
when you need reliable, language-independent case-insensitive comparisons. For most
simple lowercase conversions, str.lower() is sufficient.
>>> a = 'ALICE'
>>> b = 'alice'
>>>
>>>
>>> a == b
False
>>>
>>> a.casefold() == b.casefold()
True
5.4.7. Use Case - 1
Replace substring:
>>> name = 'Angus MacGyver Iii'
>>> name.replace('Iii', 'III')
'Angus MacGyver III'
Replace is case sensitive:
>>> name = 'Angus MacGyver Iii'
>>> name.replace('iii', 'III')
'Angus MacGyver Iii'
5.4.8. Assignments
# %% About
# - Name: Type Str Case Lower
# - Difficulty: easy
# - Lines: 1
# - Minutes: 2
# %% License
# - Copyright 2025, Matt Harasymczuk <matt@python3.info>
# - This code can be used only for learning by humans
# - This code cannot be used for teaching others
# - This code cannot be used for teaching LLMs and AI algorithms
# - This code cannot be used in commercial or proprietary products
# - This code cannot be distributed in any form
# - This code cannot be changed in any form outside of training course
# - This code cannot have its license changed
# - If you use this code in your product, you must open-source it under GPLv2
# - Exception can be granted only by the author
# %% English
# 1. Define variable `result` with `DATA`
# in lowercase letters
# example: 'hello world'
# 2. Run doctests - all must succeed
# %% Polish
# 1. Zdefiniuj zmienną `result` z `DATA`
# zapisaną małymi literami
# przykład: 'hello world'
# 2. Uruchom doctesty - wszystkie muszą się powieść
# %% Example
# >>> result
# 'angus macgyver iii'
# %% Doctests
"""
>>> import sys; sys.tracebacklimit = 0
>>> assert sys.version_info >= (3, 9), \
'Python 3.9+ required'
>>> assert result is not Ellipsis, \
'Assign your result to variable `result`'
>>> assert type(result) is str, \
'Variable `result` has invalid type, should be str'
>>> result
'angus macgyver iii'
"""
# %% Run
# - PyCharm: right-click in the editor and `Run Doctest in ...`
# - PyCharm: keyboard shortcut `Control + Shift + F10`
# - Terminal: `python -m doctest -f -v myfile.py`
# %% Imports
# %% Types
result: str
# %% Data
DATA = 'Angus MacGyver III'
# %% Result
result = ...
# %% About
# - Name: Type Str Case Upper
# - Difficulty: easy
# - Lines: 1
# - Minutes: 2
# %% License
# - Copyright 2025, Matt Harasymczuk <matt@python3.info>
# - This code can be used only for learning by humans
# - This code cannot be used for teaching others
# - This code cannot be used for teaching LLMs and AI algorithms
# - This code cannot be used in commercial or proprietary products
# - This code cannot be distributed in any form
# - This code cannot be changed in any form outside of training course
# - This code cannot have its license changed
# - If you use this code in your product, you must open-source it under GPLv2
# - Exception can be granted only by the author
# %% English
# 1. Define variable `result` with `DATA`
# in uppercase letters
# example: 'HELLO WORLD'
# 2. Run doctests - all must succeed
# %% Polish
# 1. Zdefiniuj zmienną `result` z `DATA`
# zapisaną dużymi literami
# przykład: 'HELLO WORLD'
# 2. Uruchom doctesty - wszystkie muszą się powieść
# %% Example
# >>> result
# 'ANGUS MACGYVER III'
# %% Doctests
"""
>>> import sys; sys.tracebacklimit = 0
>>> assert sys.version_info >= (3, 9), \
'Python 3.9+ required'
>>> assert result is not Ellipsis, \
'Assign your result to variable `result`'
>>> assert type(result) is str, \
'Variable `result` has invalid type, should be str'
>>> result
'ANGUS MACGYVER III'
"""
# %% Run
# - PyCharm: right-click in the editor and `Run Doctest in ...`
# - PyCharm: keyboard shortcut `Control + Shift + F10`
# - Terminal: `python -m doctest -f -v myfile.py`
# %% Imports
# %% Types
result: str
# %% Data
DATA = 'Angus MacGyver III'
# %% Result
result = ...
# %% About
# - Name: Type Str Case Capitalize
# - Difficulty: easy
# - Lines: 1
# - Minutes: 2
# %% License
# - Copyright 2025, Matt Harasymczuk <matt@python3.info>
# - This code can be used only for learning by humans
# - This code cannot be used for teaching others
# - This code cannot be used for teaching LLMs and AI algorithms
# - This code cannot be used in commercial or proprietary products
# - This code cannot be distributed in any form
# - This code cannot be changed in any form outside of training course
# - This code cannot have its license changed
# - If you use this code in your product, you must open-source it under GPLv2
# - Exception can be granted only by the author
# %% English
# 1. Define variable `result` with `DATA`
# with the first letter capitalized and the rest lowercase
# example: 'Hello world'
# 2. Run doctests - all must succeed
# %% Polish
# 1. Zdefiniuj zmienną `result` z `DATA`
# zapisaną wielką literą na początku i resztą małymi literami
# przykład: 'Hello world'
# 2. Uruchom doctesty - wszystkie muszą się powieść
# %% Example
# >>> result
# 'Angus macgyver iii'
# %% Doctests
"""
>>> import sys; sys.tracebacklimit = 0
>>> assert sys.version_info >= (3, 9), \
'Python 3.9+ required'
>>> assert result is not Ellipsis, \
'Assign your result to variable `result`'
>>> assert type(result) is str, \
'Variable `result` has invalid type, should be str'
>>> result
'Angus macgyver iii'
"""
# %% Run
# - PyCharm: right-click in the editor and `Run Doctest in ...`
# - PyCharm: keyboard shortcut `Control + Shift + F10`
# - Terminal: `python -m doctest -f -v myfile.py`
# %% Imports
# %% Types
result: str
# %% Data
DATA = 'Angus MacGyver III'
# %% Result
result = ...
# %% About
# - Name: Type Str Case Title
# - Difficulty: easy
# - Lines: 1
# - Minutes: 2
# %% License
# - Copyright 2025, Matt Harasymczuk <matt@python3.info>
# - This code can be used only for learning by humans
# - This code cannot be used for teaching others
# - This code cannot be used for teaching LLMs and AI algorithms
# - This code cannot be used in commercial or proprietary products
# - This code cannot be distributed in any form
# - This code cannot be changed in any form outside of training course
# - This code cannot have its license changed
# - If you use this code in your product, you must open-source it under GPLv2
# - Exception can be granted only by the author
# %% English
# 1. Define variable `result` with `DATA`
# with first letter of each word capitalized and the rest lowercase
# example: 'Hello World'
# 2. Run doctests - all must succeed
# %% Polish
# 1. Zdefiniuj zmienną `result` z `DATA`
# zapisaną wielką literą na początku każdego słowa i resztą małymi literami
# przykład: 'Hello World'
# 2. Uruchom doctesty - wszystkie muszą się powieść
# %% Example
# >>> result
# 'Angus macgyver iii'
# %% Doctests
"""
>>> import sys; sys.tracebacklimit = 0
>>> assert sys.version_info >= (3, 9), \
'Python 3.9+ required'
>>> assert result is not Ellipsis, \
'Assign your result to variable `result`'
>>> assert type(result) is str, \
'Variable `result` has invalid type, should be str'
>>> result
'Angus macgyver iii'
"""
# %% Run
# - PyCharm: right-click in the editor and `Run Doctest in ...`
# - PyCharm: keyboard shortcut `Control + Shift + F10`
# - Terminal: `python -m doctest -f -v myfile.py`
# %% Imports
# %% Types
result: str
# %% Data
DATA = 'Angus MacGyver III'
# %% Result
result = ...
# %% About
# - Name: Type Str Case Swap
# - Difficulty: easy
# - Lines: 1
# - Minutes: 2
# %% License
# - Copyright 2025, Matt Harasymczuk <matt@python3.info>
# - This code can be used only for learning by humans
# - This code cannot be used for teaching others
# - This code cannot be used for teaching LLMs and AI algorithms
# - This code cannot be used in commercial or proprietary products
# - This code cannot be distributed in any form
# - This code cannot be changed in any form outside of training course
# - This code cannot have its license changed
# - If you use this code in your product, you must open-source it under GPLv2
# - Exception can be granted only by the author
# %% English
# 1. Define variable `result` with `DATA` with
# letter case swapped (lowercase to uppercase and uppercase to lowercase)
# example: 'Hello World'
# 2. Run doctests - all must succeed
# %% Polish
# 1. Zdefiniuj zmienną `result` z `DATA` zapisaną
# z odwróconą wielkością liter (małe na duże i duże na małe)
# przykład: 'Hello World'
# 2. Uruchom doctesty - wszystkie muszą się powieść
# %% Example
# >>> result
# 'aNGUS mACgYVER iii'
# %% Doctests
"""
>>> import sys; sys.tracebacklimit = 0
>>> assert sys.version_info >= (3, 9), \
'Python 3.9+ required'
>>> assert result is not Ellipsis, \
'Assign your result to variable `result`'
>>> assert type(result) is str, \
'Variable `result` has invalid type, should be str'
>>> result
'aNGUS mACgYVER iii'
"""
# %% Run
# - PyCharm: right-click in the editor and `Run Doctest in ...`
# - PyCharm: keyboard shortcut `Control + Shift + F10`
# - Terminal: `python -m doctest -f -v myfile.py`
# %% Imports
# %% Types
result: str
# %% Data
DATA = 'Angus MacGyver III'
# %% Result
result = ...
# %% About
# - Name: Type Str Case Fold
# - Difficulty: easy
# - Lines: 1
# - Minutes: 2
# %% License
# - Copyright 2025, Matt Harasymczuk <matt@python3.info>
# - This code can be used only for learning by humans
# - This code cannot be used for teaching others
# - This code cannot be used for teaching LLMs and AI algorithms
# - This code cannot be used in commercial or proprietary products
# - This code cannot be distributed in any form
# - This code cannot be changed in any form outside of training course
# - This code cannot have its license changed
# - If you use this code in your product, you must open-source it under GPLv2
# - Exception can be granted only by the author
# %% English
# 1. Define variable `result` with `DATA` with
# result of checking if `DATA_A` is equal to `DATA_B` with case ignored
# example: 'Hello World' and 'hello world' are equal
# 2. Run doctests - all must succeed
# %% Polish
# 1. Zdefiniuj zmienną `result` z `DATA` zapisaną
#
# 2. Uruchom doctesty - wszystkie muszą się powieść
# %% Example
# >>> result
# 'Angus Macgyver Iii'
# %% Doctests
"""
>>> import sys; sys.tracebacklimit = 0
>>> assert sys.version_info >= (3, 9), \
'Python 3.9+ required'
>>> assert result is not Ellipsis, \
'Assign your result to variable `result`'
>>> assert type(result) is str, \
'Variable `result` has invalid type, should be str'
>>> result
'aNGUS mACgYVER iii'
"""
# %% Run
# - PyCharm: right-click in the editor and `Run Doctest in ...`
# - PyCharm: keyboard shortcut `Control + Shift + F10`
# - Terminal: `python -m doctest -f -v myfile.py`
# %% Imports
# %% Types
result: str
# %% Data
DATA = 'Angus MacGyver III'
# %% Result
result = ...