Python Practice › Exception Handling Programs › Program 20

Exception hierarchy order

EasyException Handling Programs · 20 of 20

Write a Python program showing why specific exceptions must be caught before general ones.

Output

True True
specific handler: file not found

Approach

FileNotFoundError is a subclass of OSError, so it must come first.

Solution

Python

print(issubclass(FileNotFoundError, OSError), issubclass(OSError, Exception))try:    open("nope.txt")except FileNotFoundError:    print("specific handler: file not found")except OSError:    print("general handler: some OS error")

Output

True True
specific handler: file not found

Line by line

Line 1

Python checks except blocks top to bottom and uses the first that matches, so a general OSError first would hide the specific one.

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