edn-format

library0.8.0pypypi✓ verified 23d ago

edn-format is a Python library that implements the Extensible Data Notation (EDN) format, providing functionalities to read (loads, loads_all) and write (dumps) EDN data, including support for custom tagged elements. The current version, 0.7.5, was released in November 2020, and the project is considered stable and actively maintained on GitHub, despite a less frequent release cadence.

serialization

pip install edn-format

github ↗package ↗

INSTALL

IMPORT

SIG · EDN-FORMAT

edn-format

serializationpythonv0.8.0

Install

1.8s avg

Import

152ms

Disk

19MB

Pass rate

10/ 10

Env Coverage10 / 10

glibc

3.9–3.13

musl

3.9–3.13

Install & Compatibility

Where this runs

tested against v0.8.0 · pip install

no network on importno background threads

Install × environment matrix

Each cell = how many times install + import succeeded across repeated harness runs. Partial = flaky.
glibc = Debian/Ubuntu slim · musl = Alpine Linux

musl

py 3.10–3.95 runs

installs and imports cleanly · install 0.0s · import 0.158s · 21.1MB

glibc

py 3.10–3.95 runs

installs and imports cleanly · install 1.8s · import 0.146s · 22MB

19MB installed

● package 19MB

Code

Verified usage

Verified import paths — ran on the pinned version, not inferred.

edn_format.loads

✓ import edn_format edn_format.loads("[1 2 3]")

edn_format.dumps

✓ import edn_format edn_format.dumps([1, 2, 3])

edn_format.loads_all

✓ import edn_format edn_format.loads_all("1 2 3")

edn_format.Keyword

✓ import edn_format edn_format.Keyword("my-key")

✗ ':my-key'

To explicitly create an EDN keyword in Python for dumping, use edn_format.Keyword.

edn_format.Char

✓ import edn_format edn_format.Char("\n")

✗ '\n'

Use edn_format.Char to represent EDN character literals. It subclasses Python's `str`.

This quickstart demonstrates how to serialize Python dictionaries containing various EDN types (keywords, sets, booleans, character literals) into an EDN string using `edn_format.dumps`, and then deserialize an EDN string back into Python data using `edn_format.loads`. It highlights the use of `edn_format.Keyword` and `edn_format.Char` for explicit EDN type representation.

import edn_format # Define some Python data python_data = { edn_format.Keyword('name'): 'Alice', edn_format.Keyword('age'): 30, edn_format.Keyword('tags'): {'python', 'edn'}, edn_format.Keyword('active?'): True, edn_format.Keyword('notes'): edn_format.Char('\n') # Example of EDN char literal } # Dump Python data to EDN string edn_string = edn_format.dumps(python_data, sort_keys=True, indent=2) print("--- EDN Output ---") print(edn_string) # Expected output might look like: # { # :active? true, # :age 30, # :name "Alice", # :notes \newline, # :tags #{"edn" "python"} # } # Load EDN string back to Python data edn_input = "{ :id 123 :items [\"apple\" \"banana\"] :metadata #myapp/custom {\"version\" \"1.0\"} }" loaded_data = edn_format.loads(edn_input) print("\n--- Loaded Python Data ---") print(loaded_data) # Example of accessing loaded data # print(loaded_data[edn_format.Keyword('id')]) # 123 # print(loaded_data[edn_format.Keyword('items')]) # ['apple', 'banana']

Debug

Known issues

gotchaThe library, following EDN's rationale, aims to yield immutable Python data structures (e.g., tuples for lists, frozensets for sets, ImmutableDict for maps) where possible. This can be unexpected for Python developers accustomed to mutable lists and dictionaries.

fix

Be aware that modifying returned collections might not be possible directly. Convert to mutable types (e.g., `list(immutable_list)`) if mutation is required.

affects: All versions

gotchaWhen serializing Python dictionaries, string keys will be dumped as EDN strings, not EDN keywords. To output EDN keywords for dictionary keys, you must explicitly use `edn_format.Keyword('your-key')` as the Python dictionary key.

fix

Use `edn_format.Keyword()` for dictionary keys if EDN keyword output is desired. Example: `edn_format.dumps({edn_format.Keyword('my-key'): 'value'})` will output `:my-key "value"`.

affects: All versions

gotchaEDN is a human-readable data format, and implementations like `edn-format` may not offer the same performance characteristics (speed and memory usage) as highly optimized binary serialization formats or even standard JSON libraries for high-throughput data transfer scenarios. For wire protocols, alternatives like Cognitect Transit might be more suitable.

fix

Evaluate performance requirements. For high-performance serialization, consider formats and libraries designed for that purpose. For durable storage or human-readable configurations, `edn-format` is generally suitable.

affects: All versions

gotchaWhile `edn-format` supports custom tagged literals, correctly implementing and registering reader/writer handlers for them can be complex and requires a good understanding of both the EDN specification and the library's extension mechanisms.

fix

Refer to the library's documentation or source for examples on how to register custom tag handlers (`edn_format.add_tag`). Ensure consistency between reading and writing implementations of custom types.

affects: All versions

Errors

Common errors & fixes

ModuleNotFoundError: No module named 'edn'

The user is attempting to import the `edn-format` library using a shortened name (`edn`) instead of its correct package name (`edn_format`).

fix

Use the correct package name `edn_format` for importing, typically `import edn_format` or `from edn_format import loads, dumps`.

WARNING: Couldn't open 'parser.out'. [Errno 30] Read-only file system: '.../edn_format/parser.out'

The `edn-format` library, which uses PLY, attempts to create or write cached parser tables (`parser.out`, `edn_format.parsetab`) in its installation directory. This error occurs in read-only environments (e.g., Docker containers, some virtual environments, or system-wide installations without write permissions).

fix

These are generally warnings and often don't prevent the library from working. To prevent them, ensure the environment has write permissions during the initial import/use of `edn_format`, or pre-generate the parser tables in a writable environment before deploying to a read-only one. Setting the `PYTHONHASHSEED` environment variable to a fixed value can also help with consistent `parsetab.py` generation.

edn_format.exceptions.EDNParseError: Expected ... but got ...

The input EDN string provided to `edn_format.loads()` or `edn_format.loads_all()` is syntactically incorrect or malformed according to the EDN specification, such as having unclosed delimiters, misplaced commas, or invalid characters.

fix

Carefully inspect the EDN input string for syntax errors. Ensure all opening delimiters like `(`, `[`, `{`, `#_`, `#` have their corresponding closing characters and that the data structure adheres to EDN rules for elements like keywords, symbols, and tagged elements.

Python dictionary string keys are not converted to EDN keywords/symbols when using `edn_format.dumps()`.

By default, `edn_format.dumps()` serializes Python dictionary string keys directly as EDN strings, not as Clojure-style EDN keywords (e.g., `:key`) or symbols (e.g., `key`).

fix

To output EDN keywords or symbols, explicitly convert the Python string keys to `edn_format.Keyword` or `edn_format.Symbol` objects before passing the dictionary to `edn_format.dumps()`. For example, `edn_format.dumps({edn_format.Keyword('mykey'): 'value'})`.

Incorrectly handling or reading custom EDN tagged elements.

When `edn-format` encounters a custom tagged element (e.g., `#myapp/Person {:name "Alice"}`), it either represents it as a generic `edn_format.TaggedElement` object or raises an error if no custom reader function has been registered for that specific tag.

fix

Register a custom function to handle specific EDN tags using `edn_format.add_tag(tag_name, handler_function)`. The handler function will receive the value of the tagged element and should return the desired Python object representation.

Upgrade

Version history

0.8.0latest on PyPI · released Jul 21, 2026

Audit

Dependencies

No dependency data recorded yet.

Agent activity

9 hits · last 30 days

node

Resources

githubhttps://github.com/swaroopch/edn_format ↗

packagehttps://pypi.org/project/edn-format/ ↗