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pyvalid is a Python validation tool for checking of input function parameters and return values.

Project description

Python validation tool, which is used for checking function’s input parameters and return values. Module consists of two decorators: accepts and returns.


A decorator for validating types and values of input parameters of a given function. You can pass the set of accepted types and values as decorator’s input parameters. Validation process can raise the following exceptions:

  • pyvalid.InvalidArgumentNumberError — when the number or position of arguments supplied to a function is incorrect.
  • pyvalid.ArgumentValidationError — when the type of an argument to a function is not what it should be.


A decorator for validating the return value of a given function. You can pass the set of accepted types and values as a decorator’s input parameters. Validation process can raise pyvalid.InvalidReturnType when the return value is not in the collection of supported values and types.

How to install

  • With PyPI: pip install -U pyvalid
  • Manually: python install

Example of usage

Function calc in example below has next limitations:

  • Can return only int or float value;
  • First parameter must be only of type str;
  • Second parameter must be of type int or equals to 2.0;
  • Third parameter must be of type int or float.
from pyvalid import accepts, returns

@returns(int, float)
@accepts(str, (int, 2.0), (int, float))
def calc(operator, val1, val2, val3):
    expression = '{v1} {op} {v2} {op} {v3}'.format(
        v1=val1, v2=val2, v3=val3
    return eval(expression)

# Returns int value: 24.
print(calc('*', 2, 3, 4))

# Returns float value: 24.0.
print(calc(operator='*', val1=2, val2=3.0, val3=4))

# Returns float value: 24.0.
print(calc('*', 2.0, 3, 4))

# Raise pyvalid.ArgumentValidationError exception,
# because second argument has unsupported value.
print(calc('*', 3.14, 3, 4))

# Raise pyvalid.InvalidReturnType exception,
# because returns value is of type str.
print(calc('*', 2, 3, '"4"'))

Here is an example of usage pyvalid module in context of classes.

from pyvalid import accepts, returns
from collections import Iterable

class SqlDriver(object):

    @accepts(object, str, int, str, str, str)
    def connect(self, host, port, user, password, database):
        return True

    def close(self):
        return True

    @returns(None, dict)
    @accepts(object, str, Iterable)
    def query(self, sql, params=None):
        return None

sql_driver = SqlDriver()

sql_driver.connect('', 1433, 'admin', 'password', 'programming')

sql = r'SELECT * FROM ProgrammingLang'
pl = sql_driver.query(sql)

sql = r'SELECT * FROM ProgrammingLang WHERE name=?'
python_pl = sql_driver.query(sql, ('Python',))


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Filename, size & hash SHA256 hash help File type Python version Upload date
pyvalid-0.3.tar.gz (4.9 kB) Copy SHA256 hash SHA256 Source None Aug 28, 2014

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