Handling Invalid Type Errors in Python Using Try and Except Statements
Although TypedDict may not be capable of representing every type, it can be useful when dealing with a limited number of types. If you encounter an invalid syntax error, make sure to include it under the try block. It is unfortunate that recursive types are not currently supported by mypy and the Python typing ecosystem.
Why does except not allow me to enter correct value after catching error?
- Your conditional statement is inaccurate.
- Instead of crafting a fresh message, output the message produced while raising the exception.
while True: # Input and validation of 'action' try: action = int(input('Please enter what you would like to do: ')) if action < 0: negativeError = ValueError('This value is negative') raise negativeError if not (action == 1 or action == 6): invalidValueError = ValueError('Not a valid option') raise invalidValueError break except (ValueError,TypeError ) as e: print(e) I think it should look like this:
while True: # Input and validation of 'action' try: action = int(input('Please enter what you would like to do: ')) if action < 0: negativeError = ValueError('This value is negative') raise negativeError if action not in [1, 6]: invalidValueError = ValueError('Not a valid option') raise invalidValueError break except ValueError or TypeError: print('That is invalid, please enter a valid number corresponding to one of the actions above') continue The condition of action being not equal to 1 or 6 will always hold true.
Consider using the following approach, which involves setting a default parameter value that can be adjusted later on by the caller. This way, there won't be any need to modify the code at a later stage.
def get_action(valid_actions=[1,6]): action_list = ','.join(map(str, valid_actions)) while True: try: input_ = input(f'Please select an action from this list : ') response = int(input_) if response in valid_actions: return response raise ValueError except ValueError: print('Invalid response. Try again') get_action() Afterwards, you may consider including an additional step, such as step 3.
What error to raise when class state is invalid?, RuntimeError is a more general exception and it should be used when a piece of code cannot behave correctly even if it was given proper input,
Invalid Syntax on Except TypeError?
score = float(input("What is your score?\n")) try: if score > 100 or score < 0: print("please enter a score between 100 and 0") elif score >= 80: print("GPA is 8.0 and Grade is A+") elif score >= 70: print("GPA is 7.0 and Grade is A") elif score >= 65: print("GPA is 6.5 and Grade is B") elif score >= 60: print("GPA is 6.0 and Grade is C") elif score >= 55: print("GPA is 5.5 and Grade is D") elif score >= 50: print("GPA is 5.0 and Grade is E") else: print("GPA is 0 and Grade is O") except TypeError: print("Please enter your score in digits") The reason for the invalid syntax is that 'except' needs to be placed directly underneath 'try', which was not done in this case.
Handling TypeError Exception in Python, TypeError is one among the several standard Python exceptions. TypeError is raised whenever an operation is performed on an
"invalid type" error in self-referential mypy types
Regrettably, recursive types are not currently supported by mypy and the Python typing ecosystem.
The issue can be located at https://github.com/python/mypy/issues/731, but please disregard certain posts in the middle as they were written by individuals who experienced a separate issue.
The primary obstacle mentioned in the thread, which suggests implementing structural subtyping as a priority, is currently being actively developed. It is expected to be a part of at least mypy in the coming months. Therefore, it may be worthwhile to reopen the discussion.
A common approach that individuals often adopt, primarily when typing JSON that resembles your types, is to manually expand the recursive type until reaching the desired level and eventually bottoming out with Any . An illustration of this method is as follows:
from typing import Union, Dict, List, Any KRPCTypes = Union[int, bytes, list, Dict[bytes, Union[int, bytes, list, Any]]] KRPCDict = Dict[bytes, KRPCTypes] It may be helpful to utilize typing.List[T] and indicate the intended contents of the list. In case only list is used, the default value will be typing.List[Any] , which may not be as accurate.
One possible solution is to utilize the experimental TypedDict format. This allows for the precise definition of a specific dictionary's types and structure. While TypedDict cannot represent every type of KRPCDict , the TypedDict approach is beneficial when dealing with a limited number of various KRPCDict types.
Information related to TypedDict is not available in any documentation yet. The developers are working on fixing all the major issues before they make it public. However, if you wish to experiment with it, I have included an example of how to use it at the end of this answer, which is mostly unrelated.