gpf.common.validate module

The validate module can be used to verify if certain values are “truthy”. Most of the functions in this module return a boolean (True/False).

Exceptions to this rule are the pass_if() and raise_if() functions, which can be used for data assertions and therefore serve as an alternative to the assert statement (which should not be used in production environments).

>>> def test(text):
>>>     pass_if(isinstance(text, str), TypeError, 'test() requires text input')
>>>     print(text)
>>>
>>> test('Hello World')
'Hello World'
>>>
>>> test(123)
Traceback (most recent call last):
  File "<input>", line 1, in <module>
TypeError: test() requires text input
gpf.common.validate.is_text(value: Any, allow_empty: bool = True) → bool[source]

Returns True if value is a str instance.

Parameters:
  • value – The value to check.
  • allow_empty – If True (default), empty string values are allowed. If False, empty strings will evaluate as “falsy”.
gpf.common.validate.is_number(value: Any, allow_bool: bool = False) → bool[source]

Returns True if value is a built-in numeric object (e.g. int, float, long, Decimal, etc.).

Note that is_number() will return False for booleans by default, which is non-standard behaviour, because bool is a subclass of int:

>>> isinstance(True, int)
True
>>> is_number(True)
False
Parameters:
  • value – The value to check.
  • allow_bool – If the standard Python boolean evaluation behavior is desired, set this to True.
gpf.common.validate.is_iterable(value: Any) → bool[source]

Returns True if value is an iterable container (e.g. list or tuple but not a generator).

Note that is_iterable() will return False for string-like objects as well, even though they are iterable. The same applies to generators and sets:

>>> my_list = [1, 2, 3]
>>> is_iterable(my_list)
True
>>> is_iterable(set(my_list))
False
>>> is_iterable(v for v in my_list)
False
>>> is_iterable(str(my_list))
False
Parameters:value – The value to check.
gpf.common.validate.is_guid(value: Any) → bool[source]

Returns True when the given value is a GUID-like object and False otherwise. The function effectively tries to parse the value as a gpf.tools.guids.Guid object.

Parameters:value – A string or a GUID-like object.
gpf.common.validate.has_value(obj: Any, strip: bool = False) → bool[source]

Returns True when obj is “truthy”.

Note that has_value() will return True for the False boolean and 0 integer values. Python normally evaluates these values as “falsy”, but for databases for example, these values are perfectly valid. This is why has_value() considers them to be “truthy”:

>>> my_int = 0
>>> my_bool = False
>>> if not (my_int and my_bool):
>>>     print('Both values are "falsy".')
'Both values are "falsy".'
>>> has_value(my_int)
True
>>> has_value(my_bool)
True

Other usage examples:

>>> has_value(None)
False
>>> has_value({})
False
>>> has_value('test')
True
>>> has_value('   ', strip=True)
False
Parameters:
  • obj – The object for which to evaluate its value.
  • strip – If True and obj is a str, obj will be stripped before evaluation. Defaults to False.
gpf.common.validate.signature_matches(func: Callable, template_func: Callable) → bool[source]

Checks if the given func (function or instancemethod) has a signature equal to template_func. If the function is not callable or the signature does not match, False is returned.

Parameters:
  • func – A callable function or (instance) method.
  • template_func – A template function to which the callable function argument count should be compared. This should not be a an instance method.
Return type:

bool
gpf.common.validate.pass_if(expression: Any, exc_type: type, exc_val: Any = '') → bool[source]

Raises an error of type err_type when expression is falsy and silently passes otherwise. Opposite of raise_if().

Parameters:
  • expression – An expression or value to evaluate.
  • exc_type – The error to raise when expression evaluates to False, e.g. AttributeError.
  • exc_val – An optional message or exception value to include with the error (recommended).
Examples:
>>> my_value = 0
>>> pass_if(my_value)
Traceback (most recent call last):
  File "<input>", line 1, in <module>
AssertionError
>>> pass_if(my_value == 0)
>>> pass_if(my_value == 1, ValueError, 'my_value should be 1')
Traceback (most recent call last):
  File "<input>", line 1, in <module>
ValueError: my_value should be 1
gpf.common.validate.raise_if(expression: Any, exc_type: type, exc_val: Any = '') → bool[source]

Raises an error of type err_type when expression is truthy and silently passes otherwise. Opposite of pass_if().

Parameters:
  • expression – An expression or value to evaluate.
  • exc_type – The error to raise when expression evaluates to True, e.g. AttributeError.
  • exc_val – An optional message or exception value to include with the error (recommended).
Examples:
>>> my_value = 0
>>> raise_if(my_value)
>>> raise_if(my_value == 1)
>>> raise_if(my_value == 0, ValueError, 'my_value should not be 0')
Traceback (most recent call last):
  File "<input>", line 1, in <module>
ValueError: my_value should not be 0