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A lightweight YAML Parser for Python. 🐓

Project description


A lightweight YAML Parser for Python. 🐓

poyo does not allow deserialization of arbitrary Python objects. Supported types are str, bool, int, float, NoneType as well as dict and list values.

⚠️ Please note that poyo supports only a chosen subset of the YAML format that is required to parse cookiecutter user configuration files. poyo does not have support for serializing into YAML and is not compatible with JSON.


poyo is available on PyPI for Python versions 2.7 and newer and can be installed with pip:

pip install poyo

This package does not have any additional requirements. 📦


poyo comes with a parse_string() function, to load utf-8 encoded string data into a Python dict.

import codecs
import logging

from poyo import parse_string, PoyoException


with"tests/foobar.yml", encoding="utf-8") as ymlfile:
    ymlstring =

    config = parse_string(ymlstring)
except PoyoException as exc:


Input YAML string

default_context: # foobar
    greeting: こんにちは
    email: ""
    docs: true

    gui: FALSE
    123: 456.789
    # comment
    # allthethings
    'some:int': 1000000
    foo: "hallo #welt" #Inline comment :)
    longtext: >
        This is a multiline string.
        It can contain all manners of characters.

        Single line breaks are ignored,
        but blank linkes cause line breaks.
    trueish: Falseeeeeee
    blog   :
    relative-root: /          # web app root path (default: '')
    lektor:      # local build
        # docs or didn't happen
        -    mkdocs
        - 'sphinx'

        - null
    # 今日は
zZz: True
NullValue: Null

# Block
# Comment

Hello World:
    # See you at EuroPython
    null: This is madness   # yo
"Yay #python": Cool!

Output Python dict

    u"default_context": {
        u"greeting": u"こんにちは",
        u"email": u"",
        u"docs": True,
        u"gui": False,
        u"lektor": "",
        u"relative-root": "/",
        123: 456.789,
        u"some:int": 1000000,
        u"foo": u"hallo #welt",
        u"longtext": (
            u"This is a multiline string. It can contain all "
            u"manners of characters.\nSingle line breaks are "
            u"ignored, but blank linkes cause line breaks.\n"
        u"trueish": u"Falseeeeeee",
        u"blog": u"",
        u"doc_tools": [u"mkdocs", u"sphinx", None],
    u"zZz": True,
    u"NullValue": None,
    u"Hello World": {
        None: u"This is madness",
        u"gh": u"{0}.git",
    u"Yay #python": u"Cool!",


poyo follows the recommendations for logging in a library, which means it does not configure logging itself. Its root logger is named poyo and the names of all its children loggers track the package/module hierarchy. poyo logs to a NullHandler and solely on DEBUG level.

If your application configures logging and allows debug messages to be shown, you will see logging when using poyo. The log messages indicate which parser method is used for a given string as the parser deseralizes the config. You can remove all logging from poyo in your application by setting the log level of the poyo logger to a value higher than DEBUG.

Disable Logging

import logging


Example Debug Logging Config

import logging
from poyo import parse_string


CONFIG = """
default_context: # foobar
    greeting: こんにちは
    gui: FALSE
        # docs or didn't happen
        -    mkdocs
        - 'sphinx'
    123: 456.789


Example Debug Logging Messages

DEBUG:poyo.parser:parse_blankline <- \n
DEBUG:poyo.parser:parse_blankline -> IGNORED
DEBUG:poyo.parser:parse_dashes <- ---\n
DEBUG:poyo.parser:parse_dashes -> IGNORED
DEBUG:poyo.parser:parse_section <- default_context: # foobar\n
DEBUG:poyo.parser:parse_str <- default_context
DEBUG:poyo.parser:parse_str -> default_context
DEBUG:poyo.parser:parse_section -> <Section name: default_context>
DEBUG:poyo.parser:parse_simple <-     greeting: \u3053\u3093\u306b\u3061\u306f\n
DEBUG:poyo.parser:parse_str <- greeting
DEBUG:poyo.parser:parse_str -> greeting
DEBUG:poyo.parser:parse_str <- \u3053\u3093\u306b\u3061\u306f
DEBUG:poyo.parser:parse_str -> \u3053\u3093\u306b\u3061\u306f
DEBUG:poyo.parser:parse_simple -> <Simple name: greeting, value: \u3053\u3093\u306b\u3061\u306f>
DEBUG:poyo.parser:parse_simple <-     gui: FALSE\n
DEBUG:poyo.parser:parse_str <- gui
DEBUG:poyo.parser:parse_str -> gui
DEBUG:poyo.parser:parse_false <- FALSE
DEBUG:poyo.parser:parse_false -> False
DEBUG:poyo.parser:parse_simple -> <Simple name: gui, value: False>
DEBUG:poyo.parser:parse_list <-     doc_tools:\n        # docs or didn't happen\n        -    mkdocs\n        - 'sphinx'\n
DEBUG:poyo.parser:parse_str <- mkdocs
DEBUG:poyo.parser:parse_str -> mkdocs
DEBUG:poyo.parser:parse_str <- 'sphinx'
DEBUG:poyo.parser:parse_str -> sphinx
DEBUG:poyo.parser:parse_str <- doc_tools
DEBUG:poyo.parser:parse_str -> doc_tools
DEBUG:poyo.parser:parse_list -> <Simple name: doc_tools, value: ['mkdocs', 'sphinx']>
DEBUG:poyo.parser:parse_simple <-     123: 456.789\n
DEBUG:poyo.parser:parse_int <- 123
DEBUG:poyo.parser:parse_int -> 123
DEBUG:poyo.parser:parse_float <- 456.789
DEBUG:poyo.parser:parse_float -> 456.789
DEBUG:poyo.parser:parse_simple -> <Simple name: 123, value: 456.789>
DEBUG:poyo.parser:parse_simple <-     docs: true\n
DEBUG:poyo.parser:parse_str <- docs
DEBUG:poyo.parser:parse_str -> docs
DEBUG:poyo.parser:parse_true <- true
DEBUG:poyo.parser:parse_true -> True
DEBUG:poyo.parser:parse_simple -> <Simple name: docs, value: True>

About this project

We created this project to work around installation issues with a cookiecutter version that depended on existing YAML parsers for Python. For more information please check out this GitHub issue.


Would you like to contribute to poyo? You're awesome! 😃

Please check out the good first issue label for tasks, that are good candidates for your first contribution to poyo. Your contributions are greatly appreciated! Every little bit helps and credit will always be given.

Everyone interacting in the poyo project's codebases, issue trackers, chat rooms, and mailing lists is expected to follow the PyPI Code of Conduct.

Join the poyo community! 🌍🌏🌎


Distributed under the terms of the MIT license, poyo is free and open source software.

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