Type checking (raise)

check variables, stop program and give useful error message

# check if mylist is really a list

mylist=4

if not isinstance(mylist,list):

raise TypeError('mylist is not a list')

Traceback (most recent call last):

File "<stdin>", line 2, in <module>

TypeError: Mylist is not a list

# check if 'data' is numberic

data=['A','B']

if not isinstance(data,(int,float)):

raise TypeError('data is not a number')

Traceback (most recent call last):

File "<stdin>", line 2, in <module>

TypeError: data is not a number

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Python error types

Errors and Exceptions