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How to handle errors with try/except

Updated September 2026 · Beginner-friendly guide

Catch a specific exception

Put the operation that may fail in try and catch only errors you can handle. Specific catches avoid hiding programming bugs.

text = "not a number"
try:
    number = int(text)
except ValueError:
    print(f"{text!r} is not a whole number")

Use else and finally

else runs after a successful try. finally runs whether an exception occurred or not, making it suitable for cleanup.

try:
    number = int("12")
except ValueError:
    print("Invalid number")
else:
    print(number * 2)
finally:
    print("Conversion attempt finished")

Handle several expected errors

Use separate clauses when recovery differs. Capture the exception as a name when its message contains helpful details.

try:
    with open("count.txt", encoding="utf-8") as file:
        count = int(file.read())
except FileNotFoundError:
    print("count.txt is missing")
except ValueError as error:
    print("The file does not contain an integer:", error)

Raise a useful exception

Validate function inputs near the boundary and raise an exception with a clear message. Preserve the original cause with from when translating exceptions.

def percentage(part, whole):
    if whole == 0:
        raise ValueError("whole must not be zero")
    return part / whole * 100

try:
    print(percentage(4, 0))
except ValueError as error:
    print(error)

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