16.7. JSON Recap

  • JavaScript Object Notation

  • The most popular format for data exchange

  • JSON format is similar to dict notation in Python

  • Fields are always enclosed only by double quote " character

  • Instead of True there is true (lowercase)

  • Instead of False there is false (lowercase)

  • Instead of None there is null

  • list is known as array (despite the same syntax)

  • JSON has no tuple or set

  • Coma , is not allowed after the last element in list or object

  • Object of type tuple will serialize as list

  • Object of type set is not JSON serializable

  • dict is known as object (despite the same syntax)

  • Coma , is not allowed after the last element in list or object

  • camelCase is convention, although snake_case is also valid

  • Fields are always enclosed only by double quote " character

  • Unicode characters are stored as unicode entities ("cze\\u015b\\u0107")

  • JSON can be minified to save space for network transmission

  • Minified JSON is not human readable

  • Use python -m json.tool to prettify (humanize) output

16.7.1. Assignments

# %% About
# - Name: JSON File Dump
# - Difficulty: easy
# - Lines: 3
# - Minutes: 5

# %% 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. Convert data from `list[tuple]` to `list[dict]`
# 3. Use `json` module
# 4. Result write to file `FILE`
# 5. Run doctests - all must succeed

# %% Polish
# 1. Zserializuj dane ze zmiennej `DATA`
# 2. Przekonwertuj dane z `list[tuple]` to `list[dict]`
# 3. Użyj modułu `json`
# 4. Wynik zapisz do pliku `FILE`
# 5. Uruchom doctesty - wszystkie muszą się powieść

# %% Example
# >>> 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}]

# %% Hints
# - `with open(mode='wt') as file:`
# - `json.dump()`
# - `dict(zip(header,row))`

# %% 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'

>>> from pprint import pprint
>>> pprint(result, width=79)
('[{"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}]')
"""

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

header, *rows = DATA

# %% Result


# %% About
# - Name: JSON Recap Load
# - Difficulty: easy
# - Lines: 2
# - Minutes: 5

# %% License
# - Copyright 2025, Matt Harasymczuk <matt@python3.info>
# - This code can be used only for learning by humans
# - This code cannot be user 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. Convert data from `list[dict]` to `list[tuple]`
# 3. Add sorted header as a first line
# 4. Use `json` module
# 5. Result write to file `FILE`
# 6. Run doctests - all must succeed

# %% Polish
# 1. Zserializuj dane ze zmiennej `DATA`
# 2. Przekonwertuj dane z `list[dict]` to `list[tuple]`
# 3. Add posortowany nagłówek jako pierwszą linię
# 4. Użyj modułu `json`
# 5. Wynik zapisz do pliku `FILE`
# 6. Uruchom doctesty - wszystkie muszą się powieść

# %% Example
# >>> result
# [('age', 'firstname', 'lastname'),
#  (30, 'Alice', 'Apricot'),
#  (31, 'Bob', 'Banana'),
#  (32, 'Carol', 'Corn'),
#  (33, 'Dave', 'Durian'),
#  (34, 'Eve', 'Elderberry'),
#  (15, 'Mallory', 'Melon')]

# %% Hints
# - `with open(mode='rt') as file:`
# - `json.load()`
# - `dict.keys()`
# - `dict.values()`
# - `tuple()`
# - `list.append()`
# - `list.extend()`

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

>>> from os import remove
 >>> remove(FILE)

>>> assert result is not Ellipsis, \
'Assign result to variable: `result`'
>>> assert type(result) is list, \
'Variable `result` has invalid type, should be list'
>>> assert len(result) > 0, \
'Variable `result` should not be empty'
>>> assert all(type(row) is tuple for row in result), \
'Variable `result` should be a list[tuple]'

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

# %% 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: list[tuple]

# %% Data
FILE = r'_temporary.json'

with open(FILE, mode='wt') as file:
    file.write("""[
        {"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
result = ...


# %% About
# - Name: JSON Recap Blanks
# - Difficulty: medium
# - Lines: 13
# - Minutes: 13

# %% 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. Convert data from `list[dict]` to `list[tuple]`
# 3. Add sorted header as a first line
# 4. Fill missing data with value `None`
# 5. Use `json` module
# 6. Result write to file `FILE`
# 7. Run doctests - all must succeed

# %% Polish
# 1. Zserializuj dane ze zmiennej `DATA`
# 2. Przekonwertuj dane z `list[dict]` to `list[tuple]`
# 3. Add posortowany nagłówek jako pierwszą linię
# 4. Wypełnij brakujące dane wartością `None`
# 5. Użyj modułu `json`
# 6. Wynik zapisz do pliku `FILE`
# 7. Uruchom doctesty - wszystkie muszą się powieść

# %% Example
# >>> result
# [('age', 'firstname', 'lastname'),
#  (None, 'Alice', 'Apricot'),
#  (31, 'Bob', None),
#  (32, None, 'Corn'),
#  (None, 'Dave', 'Durian'),
#  (34, 'Eve', None),
#  (None, 'Mallory', None)]

# %% Hints
# - `with open(mode='rt') as file:`
# - `json.load()`
# - `dict.keys()`
# - `dict.values()`
# - `dict.get(default=None)`
# - `dict comprehension`
# - `tuple()`
# - `set()`
# - `set.update()`
# - `set.add()`
# - `sorted()`
# - `list.append()`
# - `list.extend()`

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

>>> from os import remove
>>> remove(FILE)

>>> assert result is not Ellipsis, \
'Assign result to variable: `result`'
>>> assert type(result) is list, \
'Variable `result` has invalid type, should be list'
>>> assert len(result) > 0, \
'Variable `result` should not be empty'
>>> assert all(type(row) is tuple for row in result), \
'Variable `result` should be a list[tuple]'

>>> from pprint import pprint
>>> pprint(result)
[('age', 'firstname', 'lastname'),
 (None, 'Alice', 'Apricot'),
 (31, 'Bob', None),
 (32, None, 'Corn'),
 (None, 'Dave', 'Durian'),
 (34, 'Eve', None),
 (None, 'Mallory', None)]
"""

# %% 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: list[tuple]

# %% Data
FILE = r'_temporary.json'

with open(FILE, mode='wt') as file:
    file.write("""[
        {"firstname": "Alice", "lastname": "Apricot"},
        {"firstname": "Bob", "age": 31},
        {"lastname": "Corn", "age": 32},
        {"firstname": "Dave", "lastname": "Durian"},
        {"firstname": "Eve", "age": 34},
        {"firstname": "Mallory"}
]""")

# %% Result
result = ...