Metadata-Version: 2.0
Name: parse-type
Version: 0.4.2
Summary: Simplifies to build parse types based on the parse module
Home-page: https://github.com/jenisys/parse_type
Author: Jens Engel
Author-email: jenisys@noreply.github.com
License: BSD
Download-URL: http://pypi.python.org/pypi/parse_type
Description-Content-Type: UNKNOWN
Keywords: parse,parsing
Platform: any
Classifier: Development Status :: 4 - Beta
Classifier: Environment :: Console
Classifier: Environment :: Web Environment
Classifier: Intended Audience :: Developers
Classifier: Operating System :: OS Independent
Classifier: Programming Language :: Python :: 2.7
Classifier: Programming Language :: Python :: 3.2
Classifier: Programming Language :: Python :: 3.3
Classifier: Programming Language :: Python :: 3.4
Classifier: Programming Language :: Python :: 3.5
Classifier: Programming Language :: Python :: 3.6
Classifier: Programming Language :: Python :: Implementation :: CPython
Classifier: Programming Language :: Python :: Implementation :: PyPy
Classifier: Topic :: Software Development :: Code Generators
Classifier: Topic :: Software Development :: Libraries :: Python Modules
Classifier: License :: OSI Approved :: BSD License
Requires-Python: >=2.6, !=3.0.*, !=3.1.*
Requires-Dist: parse (>=1.8)
Requires-Dist: six (>=1.11)
Requires-Dist: ordereddict; python_version < "2.7"
Requires-Dist: enum34; python_version < "3.4"
Provides-Extra: develop
Requires-Dist: coverage; extra == 'develop'
Requires-Dist: pytest (>=3.0); extra == 'develop'
Requires-Dist: pytest-cov; extra == 'develop'
Requires-Dist: tox; extra == 'develop'
Provides-Extra: docs
Requires-Dist: sphinx (>=1.2); extra == 'docs'
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`parse_type`_ extends the `parse`_ module (opposite of `string.format()`_)
with the following features:
* build type converters for common use cases (enum/mapping, choice)
* build a type converter with a cardinality constraint (0..1, 0..*, 1..*)
from the type converter with cardinality=1.
* compose a type converter from other type converters
* an extended parser that supports the CardinalityField naming schema
and creates missing type variants (0..1, 0..*, 1..*) from the
primary type converter
.. _parse_type: http://pypi.python.org/pypi/parse_type
.. _parse: http://pypi.python.org/pypi/parse
.. _`string.format()`: http://docs.python.org/library/string.html#format-string-syntax
Definitions
-------------------------------------------------------------------------------
*type converter*
A type converter function that converts a textual representation
of a value type into instance of this value type.
In addition, a type converter function is often annotated with attributes
that allows the `parse`_ module to use it in a generic way.
A type converter is also called a *parse_type* (a definition used here).
*cardinality field*
A naming convention for related types that differ in cardinality.
A cardinality field is a type name suffix in the format of a field.
It allows parse format expression, ala::
"{person:Person}" #< Cardinality: 1 (one; the normal case)
"{person:Person?}" #< Cardinality: 0..1 (zero or one = optional)
"{persons:Person*}" #< Cardinality: 0..* (zero or more = many0)
"{persons:Person+}" #< Cardinality: 1..* (one or more = many)
This naming convention mimics the relationship descriptions in UML diagrams.
Basic Example
-------------------------------------------------------------------------------
Define an own type converter for numbers (integers):
.. code-block:: python
# -- USE CASE:
def parse_number(text):
return int(text)
parse_number.pattern = r"\d+" # -- REGULAR EXPRESSION pattern for type.
This is equivalent to:
.. code-block:: python
import parse
@parse.with_pattern(r"\d+")
def parse_number(text):
return int(text)
assert hasattr(parse_number, "pattern")
assert parse_number.pattern == r"\d+"
.. code-block:: python
# -- USE CASE: Use the type converter with the parse module.
schema = "Hello {number:Number}"
parser = parse.Parser(schema, dict(Number=parse_number))
result = parser.parse("Hello 42")
assert result is not None, "REQUIRE: text matches the schema."
assert result["number"] == 42
result = parser.parse("Hello XXX")
assert result is None, "MISMATCH: text does not match the schema."
.. hint::
The described functionality above is standard functionality
of the `parse`_ module. It serves as introduction for the remaining cases.
Cardinality
-------------------------------------------------------------------------------
Create an type converter for "ManyNumbers" (List, separated with commas)
with cardinality "1..* = 1+" (many) from the type converter for a "Number".
.. code-block:: python
# -- USE CASE: Create new type converter with a cardinality constraint.
# CARDINALITY: many := one or more (1..*)
from parse import Parser
from parse_type import TypeBuilder
parse_numbers = TypeBuilder.with_many(parse_number, listsep=",")
schema = "List: {numbers:ManyNumbers}"
parser = Parser(schema, dict(ManyNumbers=parse_numbers))
result = parser.parse("List: 1, 2, 3")
assert result["numbers"] == [1, 2, 3]
Create an type converter for an "OptionalNumbers" with cardinality "0..1 = ?"
(optional) from the type converter for a "Number".
.. code-block:: python
# -- USE CASE: Create new type converter with cardinality constraint.
# CARDINALITY: optional := zero or one (0..1)
from parse import Parser
from parse_type import TypeBuilder
parse_optional_number = TypeBuilder.with_optional(parse_number)
schema = "Optional: {number:OptionalNumber}"
parser = Parser(schema, dict(OptionalNumber=parse_optional_number))
result = parser.parse("Optional: 42")
assert result["number"] == 42
result = parser.parse("Optional: ")
assert result["number"] == None
Enumeration (Name-to-Value Mapping)
-------------------------------------------------------------------------------
Create an type converter for an "Enumeration" from the description of
the mapping as dictionary.
.. code-block:: python
# -- USE CASE: Create a type converter for an enumeration.
from parse import Parser
from parse_type import TypeBuilder
parse_enum_yesno = TypeBuilder.make_enum({"yes": True, "no": False})
parser = Parser("Answer: {answer:YesNo}", dict(YesNo=parse_enum_yesno))
result = parser.parse("Answer: yes")
assert result["answer"] == True
Create an type converter for an "Enumeration" from the description of
the mapping as an enumeration class (`Python 3.4 enum`_ or the `enum34`_
backport; see also: `PEP-0435`_).
.. code-block:: python
# -- USE CASE: Create a type converter for enum34 enumeration class.
# NOTE: Use Python 3.4 or enum34 backport.
from parse import Parser
from parse_type import TypeBuilder
from enum import Enum
class Color(Enum):
red = 1
green = 2
blue = 3
parse_enum_color = TypeBuilder.make_enum(Color)
parser = Parser("Select: {color:Color}", dict(Color=parse_enum_color))
result = parser.parse("Select: red")
assert result["color"] is Color.red
.. _`Python 3.4 enum`: http://docs.python.org/3.4/library/enum.html#module-enum
.. _enum34: http://pypi.python.org/pypi/enum34
.. _PEP-0435: http://www.python.org/dev/peps/pep-0435
Choice (Name Enumeration)
-------------------------------------------------------------------------------
A Choice data type allows to select one of several strings.
Create an type converter for an "Choice" list, a list of unique names
(as string).
.. code-block:: python
from parse import Parser
from parse_type import TypeBuilder
parse_choice_yesno = TypeBuilder.make_choice(["yes", "no"])
schema = "Answer: {answer:ChoiceYesNo}"
parser = Parser(schema, dict(ChoiceYesNo=parse_choice_yesno))
result = parser.parse("Answer: yes")
assert result["answer"] == "yes"
Variant (Type Alternatives)
-------------------------------------------------------------------------------
Sometimes you need a type converter that can accept text for multiple
type converter alternatives. This is normally called a "variant" (or: union).
Create an type converter for an "Variant" type that accepts:
* Numbers (positive numbers, as integer)
* Color enum values (by name)
.. code-block:: python
from parse import Parser, with_pattern
from parse_type import TypeBuilder
from enum import Enum
class Color(Enum):
red = 1
green = 2
blue = 3
@with_pattern(r"\d+")
def parse_number(text):
return int(text)
# -- MAKE VARIANT: Alternatives of different type converters.
parse_color = TypeBuilder.make_enum(Color)
parse_variant = TypeBuilder.make_variant([parse_number, parse_color])
schema = "Variant: {variant:Number_or_Color}"
parser = Parser(schema, dict(Number_or_Color=parse_variant))
# -- TEST VARIANT: With number, color and mismatch.
result = parser.parse("Variant: 42")
assert result["variant"] == 42
result = parser.parse("Variant: blue")
assert result["variant"] is Color.blue
result = parser.parse("Variant: __MISMATCH__")
assert not result
Extended Parser with CardinalityField support
-------------------------------------------------------------------------------
The parser extends the ``parse.Parser`` and adds the following functionality:
* supports the CardinalityField naming scheme
* automatically creates missing type variants for types with
a CardinalityField by using the primary type converter for cardinality=1
* extends the provide type converter dictionary with new type variants.
Example:
.. code-block:: python
# -- USE CASE: Parser with CardinalityField support.
# NOTE: Automatically adds missing type variants with CardinalityField part.
# USE: parse_number() type converter from above.
from parse_type.cfparse import Parser
# -- PREPARE: parser, adds missing type variant for cardinality 1..* (many)
type_dict = dict(Number=parse_number)
schema = "List: {numbers:Number+}"
parser = Parser(schema, type_dict)
assert "Number+" in type_dict, "Created missing type variant based on: Number"
# -- USE: parser.
result = parser.parse("List: 1, 2, 3")
assert result["numbers"] == [1, 2, 3]