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Contracts

Python is a dynamically typed language, but each of our methods expects its arguments to be of specific types and value ranges. To avoid wrong inputs, the tracker takes two approaches:

  1. It specifies type hints on each function argument and return value. This allows IDEs to validate function calls in your code and also enables static type checking using tools such as mypy. However, type violations do not result in runtime errors.
  2. It validates expected value ranges during runtime and throws ValueError errors in case they are violated. Contracts are defined for arguments to check that they belong to expected value ranges such as:
s = Subject()
tracker.set_platform("coffee") # throws ValueError because "coffee" is not one of supported platforms
tracker.set_screen_resolution(width=-1, height=-1) # throws ValueError because width and height arguments have to be greater than 0

You can turn off runtime contract validation like this:

from snowplow_tracker import disable_contracts
disable_contracts()