I have been learning Python for a while and the raise function and assert are (what I realised is that both of them crash the app, unlike try - except) really similar and I can't see a situation where you would use raise or assert over try.
So, what is the difference between raise, try, and assert?
Assert:
Used when you want to "stop" the script based on a certain condition and return something to help debug faster:
list_ = ["a","b","x"]
assert "x" in list_, "x is not in the list"
print("passed")
#>> prints passed
list_ = ["a","b","c"]
assert "x" in list_, "x is not in the list"
print("passed")
#>>
Traceback (most recent call last):
File "python", line 2, in <module>
AssertionError: x is not in the list
Raise:
Two reasons where this is useful:
1/ To be used with try and except blocks. Raise an error of your choosing, could be custom like below and doesn't stop the script if you pass or continue the script; or can be predefined errors raise ValueError()
class Custom_error(BaseException):
pass
try:
print("hello")
raise Custom_error
print("world")
except Custom_error:
print("found it not stopping now")
print("im outside")
>> hello
>> found it not stopping now
>> im outside
Noticed it didn't stop? We can stop it using just exit(1) in the except block.
2/ Raise can also be used to re-raise the current error to pass it up the stack to see if something else can handle it.
except SomeError, e:
if not can_handle(e):
raise
someone_take_care_of_it(e)
Try/Except blocks:
Does exactly what you think, tries something if an error comes up you catch it and deal with it however you like. No example since there's one above.