• str is a sequence of characters

Example:

>>> name = 'Alice'
>>> color = 'red'
>>> text = 'Hello World'

6.1.1. Syntax

  • Str can have any length: zero, one or many characters (including spaces, etc.)

>>> data = ''
>>> data = 'a'
>>> data = 'abc'
>>> data = 'abc def'

6.1.2. Quotes or Apostrophes

  • Both quotes (") and apostrophes (') works the same

  • Choose one style and keep consistency in code

  • Python console prefers single quote (') character

  • It matters for doctest, which compares two outputs character by character

Both " and ' works the same

>>> a = 'It is Monty Python'
>>> b = "It is Monty Python"
>>>
>>> a == b
True

Python console prefers single quote (') character:

>>> data = 'It is Monty Python'
>>> data
'It is Monty Python'
>>>
>>> data = "It is Monty Python"
>>> data
'It is Monty Python'

Why we have both? It's better to use double quotes, when text has apostrophes. This is also a default the behavior of Python console, which prefers less escape characters:

>>> data = 'It\'s Monty Python'
>>> data
"It's Monty Python"
>>>
>>> data = "It's Monty Python"
>>> data
"It's Monty Python"

However HTML and XML uses double quotes to enclose attribute values, hence it's better to use single quotes for the string:

>>> data = '<img src="myfile.png">'
>>> data
'<img src="myfile.png">'
>>>
>>> data = "<img src=\"myfile.png\">"
>>> data
'<img src="myfile.png">'

Errors:

>>> data = 'It's Monty Python'
Traceback (most recent call last):
SyntaxError: unterminated string literal (detected at line 1)

>>> data = "<img src="myfile.png">"
Traceback (most recent call last):
SyntaxError: invalid syntax. Is this intended to be part of the string?

6.1.3. Newline and Tab

  • \n - New line (ENTER)

  • \t - Horizontal Tab (TAB)

>>> data = 'Hello\nWorld'
>>> print(data)
Hello
World

>>> data = 'Hello\tWorld'
>>> print(data)
Hello   World

6.1.4. Multiline Strings

  • """ - three quotes

  • ''' - three apostrophes

If assigned to variable, it serves as multiline str otherwise it's a docstring:

>>> data = """Fist line
... Second line
... Third line"""

>>> data = '''Fist line
... Second line
... Third line'''

6.1.5. Escape Characters

>>> data = 'Hello\\World'
>>> print(data)
Hello\World

>>> data = 'Hello \'World\''
>>> print(data)
Hello 'World'

>>> data = "Hello \"World\""
>>> print(data)
Hello "World"

6.1.6. Conversion

  • Builtin function str() converts argument to str

6.1.7. Unicode

  • \U - UTF-32 character codepoint (8 hex digits), example: \U0001F600

  • \u - UTF-16 character codepoint (4 hex digits), example: \uF600

  • Codepoint notation U+1F600 is the same as \U0001F600 in Python

  • You can use either codepoint \U0001F600 or emoji 😀 in your source code

  • More information in Intermediate -> Encoding -> Unicode

>>> text = 'Hello \U0001F600'
>>> print(text)
Hello 😀

>>> text = 'Hello 😀'
>>> print(text)
Hello 😀

Advanced:

>>> a = '\U0001F9D1'  # 🧑
>>> b = '\U0000200D'  # ''
>>> c = '\U0001F680'  # 🚀
>>>
>>> astronaut = a + b + c
>>> print(astronaut)
🧑‍🚀

6.1.8. Contains

  • in checks whether value is in sequence

  • O(n) - contains in str

>>> 'P' in 'Python'
True
>>>
>>> 'p' in 'Python'
False

>>> 'Python' in 'Python'
True
>>>
>>> 'Py' in 'Python'
True

6.1.9. Recap

  • str is a sequence of characters

  • Both quotes (") and apostrophes (') works the same

  • Choose one style and keep consistency in code

  • Python console prefers single quote (') character

  • Builtin function str() converts argument to str

  • \n - New line (ENTER)

  • \t - Horizontal Tab (TAB)

  • \' - Single quote ' (escape in single quoted strings)

  • \" - Double quote " (escape in double quoted strings)

  • \\ - Backslash \ (to indicate, that this is not escape char)

Definition:

>>> text = 'It is Monty Python'
>>> text = "It is Monty Python"

Quotes or apostrophes:

>>> text = "It's Monty Python"
>>> text = 'It\'s Monty Python'
>>>
>>> text = '<a href="https://python3.info">Python Book</a>'
>>> text = "<a href=\"https://python3.info\">Python Book</a>"

Newline and Tab:

>>> text = 'Hello\nWorld'
>>> text = 'Hello\tWorld'

Multiline:

>>> text = """Fist line
... Second line
... Third line"""

>>> text = '''Fist line
... Second line
... Third line'''

Longer:

>>> text = (
...     'First part '
...     'Second part '
...     'Third part'
... )

>>> text = 'First part ' \
...        'Second part ' \
...        'Third part'

Type conversion:

Unicode:

>>> text = 'Hello \U0001F600'
>>> print(text)
Hello 😀

6.1.10. Assignments

# %% About
# - Name: Type Str Define
# - Difficulty: easy
# - Lines: 1
# - Minutes: 1

# %% 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 `result1` with value `hello`, use single apostrophes
# 2. Define `result2` with value `hello`, use single quotes
# 3. Run doctests - all must succeed

# %% Polish
# 1. Zdefiniuj `result1` z wartością `hello`, użyj pojedynczych apostrofów
# 2. Zdefiniuj `result2` z wartością `hello`, użyj pojedynczych cudzysłowów
# 3. Uruchom doctesty - wszystkie muszą się powieść

# %% Expected
# >>> print(result1)
# hello
#
# >>> print(result2)
# hello

# %% Doctests
"""
>>> import sys; sys.tracebacklimit = 0

>>> assert sys.version_info >= (3, 9), \
'Python has an is invalid version; expected: `3.9` or newer.'

>>> assert 'result1' in globals(), \
'Variable `result1` is not defined; assign result of your program to it.'

>>> assert result1 is not Ellipsis, \
'Variable `result1` has an invalid value; assign result of your program to it.'

>>> assert type(result1) is str, \
'Variable `result1` has an invalid type; expected: `str`.'
>>> result1
'hello'

>>> assert 'result2' in globals(), \
'Variable `result2` is not defined; assign result of your program to it.'

>>> assert result2 is not Ellipsis, \
'Variable `result2` has an invalid value; assign result of your program to it.'

>>> assert type(result2) is str, \
'Variable `result2` has an invalid type; expected: `str`.'
>>> result2
'hello'
"""

# %% 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
result1: str
result2: str

# %% Data

# %% Result
result1 = ...
result2 = ...


# %% About
# - Name: Type Str Define
# - Difficulty: easy
# - Lines: 1
# - Minutes: 1

# %% 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 `result1` with value `hello`, use triple apostrophes
# 2. Define `result2` with value `hello`, use triple quotes
# 3. Run doctests - all must succeed

# %% Polish
# 1. Zdefiniuj `result1` z wartością `hello`, użyj potrójnych apostrofów
# 2. Zdefiniuj `result2` z wartością `hello`, użyj potrójnych cudzysłowów
# 3. Uruchom doctesty - wszystkie muszą się powieść

# %% Expected
# >>> print(result1)
# hello
#
# >>> print(result2)
# hello

# %% Doctests
"""
>>> import sys; sys.tracebacklimit = 0

>>> assert sys.version_info >= (3, 9), \
'Python has an is invalid version; expected: `3.9` or newer.'

>>> assert 'result1' in globals(), \
'Variable `result1` is not defined; assign result of your program to it.'

>>> assert result1 is not Ellipsis, \
'Variable `result1` has an invalid value; assign result of your program to it.'

>>> assert type(result1) is str, \
'Variable `result1` has an invalid type; expected: `str`.'
>>> result1
'hello'

>>> assert 'result2' in globals(), \
'Variable `result2` is not defined; assign result of your program to it.'

>>> assert result2 is not Ellipsis, \
'Variable `result2` has an invalid value; assign result of your program to it.'

>>> assert type(result2) is str, \
'Variable `result2` has an invalid type; expected: `str`.'
>>> result2
'hello'
"""

# %% 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
result1: str
result2: str

# %% Data

# %% Result
result1 = ...
result2 = ...


# %% About
# - Name: Type Str Quotes
# - Difficulty: easy
# - Lines: 1
# - Minutes: 1

# %% 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: str` with value:
#    He said: "It's Monty Python"
# 2. Run doctests - all must succeed

# %% Polish
# 1. Zdefiniuj zmienną `result: str` z wartością:
#    He said: "It's Monty Python"
# 2. Uruchom doctesty - wszystkie muszą się powieść

# %% Expected
# >>> print(result)
# He said: "It's Monty Python"

# %% Doctests
"""
>>> import sys; sys.tracebacklimit = 0

>>> assert sys.version_info >= (3, 9), \
'Python has an is invalid version; expected: `3.9` or newer.'

>>> from pprint import pprint

>>> assert 'result' in globals(), \
'Variable `result` is not defined; assign result of your program to it.'

>>> assert result is not Ellipsis, \
'Variable `result` has an invalid value; assign result of your program to it.'

>>> assert type(result) is str, \
'Variable `result` has an invalid type; expected: `str`.'

>>> print(result)
He said: "It's Monty Python"
"""

# %% 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

# %% Result
result = ...


# %% About
# - Name: Type Str Unicode
# - Difficulty: easy
# - Lines: 1
# - Minutes: 1

# %% 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 `result: str` with text: 'Hello 😀'
# 2. Unicode codepoint for smiley emoticon (😀) is '\U0001F600'
# 3. Run doctests - all must succeed

# %% Polish
# 1. Zdefiniuj `result: str` z tekstem: 'Hello 😀'
# 2. Kod znaku emotikony uśmieszek (😀) to '\U0001F600'
# 3. Uruchom doctesty - wszystkie muszą się powieść

# %% Expected
# >>> print(result)
# Hello 😀

# %% Doctests
"""
>>> import sys; sys.tracebacklimit = 0

>>> assert sys.version_info >= (3, 9), \
'Python has an is invalid version; expected: `3.9` or newer.'

>>> assert 'result' in globals(), \
'Variable `result` is not defined; assign result of your program to it.'

>>> assert result is not Ellipsis, \
'Variable `result` has an invalid value; assign result of your program to it.'

>>> assert type(result) is str, \
'Variable `result` has an invalid type; expected: `str`.'

>>> '😀' in result
True
>>> result
'Hello 😀'
"""

# %% 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

# %% Result
result = ...