16.2. JSON Dump

  • json.dumps(object) -> str - Python object to JSON string

  • json.dump(object) -> file - Python object to JSON file

  • file extension .json

16.2.1. SetUp

✘
import json

16.2.2. Sequence

✘
DATA = ('Alice', 'Apricot', 30)

result = json.dumps(DATA)

print(result)
["Alice", "Apricot", 30]

16.2.3. Mapping

✘
DATA = {'firstname': 'Alice', 'lastname': 'Apricot', 'age': 30}

result = json.dumps(DATA)

print(result)
{"firstname": "Alice", "lastname": "Apricot", "age": 30}

16.2.4. List of Sequence

✘
DATA = [
    ('firstname', 'lastname', 'age'),
    ('Alice', 'Apricot', 30),
    ('Bob', 'Banana', 31),
    ('Carol', 'Corn', 32),
    ('Dave', 'Durian', 33),
    ('Eve', 'Elderberry', 34),
    ('Mallory', 'Melon', 15),
]

result = json.dumps(DATA)

print(result)
[["firstname", "lastname", "age"],
 ["Alice", "Apricot", 30],
 ["Bob", "Banana", 31],
 ["Carol", "Corn", 32],
 ["Dave", "Durian", 33],
 ["Eve", "Elderberry", 34],
 ["Mallory", "Melon", 15]]

16.2.5. List of Mappings

✘
DATA = [
    {'firstname': 'Alice', 'lastname': 'Apricot', 'age': 30},
    {'firstname': 'Bob', 'lastname': 'Banana', 'age': 31},
    {'firstname': 'Carol', 'lastname': 'Corn', 'age': 32},
    {'firstname': 'Dave', 'lastname': 'Durian', 'age': 33},
    {'firstname': 'Eve', 'lastname': 'Elderberry', 'age': 34},
    {'firstname': 'Mallory', 'lastname': 'Melon', 'age': 15},
]

result = json.dumps(DATA)

print(result)
[{"firstname": "Alice", "lastname": "Apricot", "age": 30},
 {"firstname": "Bob", "lastname": "Banana", "age": 31},
 {"firstname": "Carol", "lastname": "Corn", "age": 32},
 {"firstname": "Dave", "lastname": "Durian", "age": 33},
 {"firstname": "Eve", "lastname": "Elderberry", "age": 34},
 {"firstname": "Mallory", "lastname": "Melon", "age": 15}]

16.2.6. To File

  • json.dump(data, file) -> None

  • file extension .json

def dump(obj: Any,
         fp: IO[str],
         *,
         skipkeys: bool = ...,
         ensure_ascii: bool = ...,
         check_circular: bool = ...,
         allow_nan: bool = ...,
         cls: type[JSONEncoder] | None = ...,
         indent: None | int | str = ...,
         separators: tuple[str, str] | None = ...,
         default: (Any) -> Any | None = ...,
         sort_keys: bool = ...,
         **kwds: Any) -> None

SetUp:

✘
DATA = {'firstname': 'Alice', 'lastname': 'Apricot', 'age': 30}

Usage:

✘
with open('/tmp/myfile.json', mode='wt') as file:
    json.dump(DATA, file)

Result:

✘
result = open('/tmp/myfile.json').read()
print(result)
{"firstname": "Alice", "lastname": "Apricot", "age": 30}

16.2.7. Assignments

# %% About
# - Name: JSON Dump Sequence
# - 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. Serialize data from variable `DATA`
# 2. Use `json` module
# 3. Result write to variable `result`
# 4. Run doctests - all must succeed

# %% Polish
# 1. Zserializuj dane ze zmiennej `DATA`
# 2. Użyj modułu `json`
# 3. Wynik zapisz do zmiennej `result`
# 4. Uruchom doctesty - wszystkie muszą się powieść

# %% Example
# >>> result
# ["Alice", "Apricot", 30]

# %% Hints
# - `json.dumps()`

# %% Doctests
"""
>>> import sys; sys.tracebacklimit = 0
>>> assert sys.version_info >= (3, 9), \
'Python 3.9+ required'

>>> assert result is not Ellipsis, \
'Assign result to variable: `result`'
>>> assert type(result) is str, \
'Variable `result` has invalid type, should be str'
>>> assert len(result) > 0, \
'Variable `result` should not be empty'

>>> print(result)
["Alice", "Apricot", 30]
"""

# %% Run
# - PyCharm: right-click in the editor and `Run Doctest in ...`
# - PyCharm: keyboard shortcut `Control + Shift + F10`
# - Terminal: `python -m doctest -v myfile.py`

# %% Imports
import json

# %% Types
result: str

# %% Data
DATA = ('Alice', 'Apricot', 30)

# %% Result
result = ...


# %% About
# - Name: JSON Dump Mapping
# - 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. Serialize data from variable `DATA`
# 2. Use `json` module
# 3. Result write to variable `result`
# 4. Run doctests - all must succeed

# %% Polish
# 1. Zserializuj dane ze zmiennej `DATA`
# 2. Użyj modułu `json`
# 3. Wynik zapisz do zmiennej `result`
# 4. Uruchom doctesty - wszystkie muszą się powieść

# %% Hints
# - `json.dumps()`

# %% Doctests
"""
>>> import sys; sys.tracebacklimit = 0
>>> assert sys.version_info >= (3, 9), \
'Python 3.9+ required'

>>> assert result is not Ellipsis, \
'Assign result to variable: `result`'
>>> assert type(result) is str, \
'Variable `result` has invalid type, should be str'
>>> assert len(result) > 0, \
'Variable `result` should not be empty'

>>> print(result)
{"firstname": "Mark", "lastname": "Watney", "age": 41}
"""

# %% Run
# - PyCharm: right-click in the editor and `Run Doctest in ...`
# - PyCharm: keyboard shortcut `Control + Shift + F10`
# - Terminal: `python -m doctest -v myfile.py`

# %% Imports
import json

# %% Types
result: str

# %% Data
DATA = {'firstname': 'Mark', 'lastname': 'Watney', 'age': 41}

# %% Result
result = ...


# %% About
# - Name: JSON Dump ListSequence
# - 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. Serialize data from variable `DATA`
# 2. Use `json` module
# 3. Result write to variable `result`
# 4. Run doctests - all must succeed

# %% Polish
# 1. Zserializuj dane ze zmiennej `DATA`
# 2. Użyj modułu `json`
# 3. Wynik zapisz do zmiennej `result`
# 4. Uruchom doctesty - wszystkie muszą się powieść

# %% Hints
# - `json.dumps()`

# %% Doctests
"""
>>> import sys; sys.tracebacklimit = 0
>>> assert sys.version_info >= (3, 9), \
'Python 3.9+ required'

>>> assert result is not Ellipsis, \
'Assign result to variable: `result`'
>>> assert type(result) is str, \
'Variable `result` has invalid type, should be str'
>>> assert len(result) > 0, \
'Variable `result` should not be empty'

>>> print(result)  # doctest: +NORMALIZE_WHITESPACE
[["firstname", "lastname", "age"],
 ["Mark", "Watney", 41],
 ["Melissa", "Lewis", 40],
 ["Rick", "Martinez", 39],
 ["Alex", "Vogel", 40],
 ["Chris", "Beck", 36],
 ["Beth", "Johanssen", 29]]
"""

# %% Run
# - PyCharm: right-click in the editor and `Run Doctest in ...`
# - PyCharm: keyboard shortcut `Control + Shift + F10`
# - Terminal: `python -m doctest -v myfile.py`

# %% Imports
import json

# %% Types
result: str

# %% Data
DATA = [
    ('firstname', 'lastname', 'age'),
    ('Mark', 'Watney', 41),
    ('Melissa', 'Lewis', 40),
    ('Rick', 'Martinez', 39),
    ('Alex', 'Vogel', 40),
    ('Chris', 'Beck', 36),
    ('Beth', 'Johanssen', 29),
]

# %% Result
result = ...


# %% About
# - Name: JSON Dump ListMapping
# - 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. Serialize data from variable `DATA`
# 2. Use `json` module
# 3. Result write to variable `result`
# 4. Run doctests - all must succeed

# %% Polish
# 1. Zserializuj dane ze zmiennej `DATA`
# 2. Użyj modułu `json`
# 3. Wynik zapisz do zmiennej `result`
# 4. Uruchom doctesty - wszystkie muszą się powieść

# %% Hints
# - `json.dumps()`

# %% Doctests
"""
>>> import sys; sys.tracebacklimit = 0
>>> assert sys.version_info >= (3, 9), \
'Python 3.9+ required'

>>> assert result is not Ellipsis, \
'Assign result to variable: `result`'
>>> assert type(result) is str, \
'Variable `result` has invalid type, should be str'
>>> assert len(result) > 0, \
'Variable `result` should not be empty'

>>> print(result)  # doctest: +NORMALIZE_WHITESPACE
[{"firstname": "Mark", "lastname": "Watney", "age": 41},
 {"firstname": "Melissa", "lastname": "Lewis", "age": 40},
 {"firstname": "Rick", "lastname": "Martinez", "age": 39},
 {"firstname": "Alex", "lastname": "Vogel", "age": 40},
 {"firstname": "Chris", "lastname": "Beck", "age": 36},
 {"firstname": "Beth", "lastname": "Johanssen", "age": 29}]
"""

# %% Run
# - PyCharm: right-click in the editor and `Run Doctest in ...`
# - PyCharm: keyboard shortcut `Control + Shift + F10`
# - Terminal: `python -m doctest -v myfile.py`

# %% Imports
import json

# %% Types
result: str

# %% Data
DATA = [
    {'firstname': 'Mark', 'lastname': 'Watney', 'age': 41},
    {'firstname': 'Melissa', 'lastname': 'Lewis', 'age': 40},
    {'firstname': 'Rick', 'lastname': 'Martinez', 'age': 39},
    {'firstname': 'Alex', 'lastname': 'Vogel', 'age': 40},
    {'firstname': 'Chris', 'lastname': 'Beck', 'age': 36},
    {'firstname': 'Beth', 'lastname': 'Johanssen', 'age': 29},
]

# %% Result
result = ...


# %% About
# - Name: JSON Dump ToFile
# - Difficulty: easy
# - Lines: 2
# - Minutes: 3

# %% 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. Serialize data from variable `DATA`
# 2. Use `json` module
# 3. Result write to file `FILE`
# 4. Run doctests - all must succeed

# %% Polish
# 1. Zserializuj dane ze zmiennej `DATA`
# 2. Użyj modułu `json`
# 3. Wynik zapisz do pliku `FILE`
# 4. Uruchom doctesty - wszystkie muszą się powieść

# %% Hints
# - `with open(mode='wt') as file:`
# - `json.dump()`

# %% Doctests
"""
>>> import sys; sys.tracebacklimit = 0
>>> assert sys.version_info >= (3, 9), \
'Python 3.9+ required'

>>> from os import remove
>>> result = open(FILE).read()
>>> remove(FILE)

>>> assert result is not Ellipsis, \
'Assign result to variable: `result`'
>>> assert type(result) is str, \
'Variable `result` has invalid type, should be str'
>>> assert len(result) > 0, \
'Variable `result` should not be empty'

>>> print(result)  # doctest: +NORMALIZE_WHITESPACE
[["sepal_length", "sepal_width", "petal_length", "petal_width", "species"],
 [5.8, 2.7, 5.1, 1.9, "virginica"],
 [5.1, 3.5, 1.4, 0.2, "setosa"],
 [5.7, 2.8, 4.1, 1.3, "versicolor"],
 [6.3, 2.9, 5.6, 1.8, "virginica"],
 [6.4, 3.2, 4.5, 1.5, "versicolor"],
 [4.7, 3.2, 1.3, 0.2, "setosa"],
 [7.0, 3.2, 4.7, 1.4, "versicolor"],
 [7.6, 3.0, 6.6, 2.1, "virginica"],
 [4.9, 3.0, 1.4, 0.2, "setosa"]]
"""

# %% Run
# - PyCharm: right-click in the editor and `Run Doctest in ...`
# - PyCharm: keyboard shortcut `Control + Shift + F10`
# - Terminal: `python -m doctest -v myfile.py`

# %% Imports
import json

# %% Types

# %% Data
FILE = '_temporary.json'

DATA = [
    ('sepal_length', 'sepal_width', 'petal_length', 'petal_width', 'species'),
    (5.8, 2.7, 5.1, 1.9, 'virginica'),
    (5.1, 3.5, 1.4, 0.2, 'setosa'),
    (5.7, 2.8, 4.1, 1.3, 'versicolor'),
    (6.3, 2.9, 5.6, 1.8, 'virginica'),
    (6.4, 3.2, 4.5, 1.5, 'versicolor'),
    (4.7, 3.2, 1.3, 0.2, 'setosa'),
    (7.0, 3.2, 4.7, 1.4, 'versicolor'),
    (7.6, 3.0, 6.6, 2.1, 'virginica'),
    (4.9, 3.0, 1.4, 0.2, 'setosa'),
]

# %% Result