Decorator that allows you to specify the valid types of the parameters in a function or method.
In case of that a call don't match the required type will fail with a
TypeError
exception.
For most cases I'd recommend using tests instead of type checking since it's more natural to do that in Python. But, there are some cases where you want/need to specify a specific type to use and since python does not have type checks for parameters here's where this is useful.
All the existing solutions that I've found had some problem or does not have a feature that I'd like to have, so I've made my own.
First, install the RequireType
package, you can do that using pip
.
$ pip install requiretype
In your code you just need to import and use the require
decorator.
Example:
from requiretype import require
@require(name=str, age=(int, float, long))
def greet_person(name, age):
print "Hello {0} ({1})".format(name, age)
>>> greet_person("John", 42)
Hello John (42)
>>> greet_person("John", "Doe")
# [...traceback...]
TypeError: Doe is not a valid type.
Valid types: <type 'int'>, <type 'float'>, <type 'long'>
>>> greet_person(42, 43)
# [...traceback...]
TypeError: 42 is not a <type 'str'> type
Here are some details about this library. Most of them was found in one or more packages that helps you to enforce/check/require types and IMO are not good things to have and motivated me to write this.
RequireType:
- does not modify
args
orkwargs
- does not move arguments from one place to another
- support both
args
andkwargs
- allows you to use all the python 2.x supported parameters usage (if not, please report a bug)
- use named arguments type definition
- allows you to enforce a subset of all the available arguments
- raise a standard
TypeError
if the arguments type are wrong