Built-in Exceptions

Exceptions which Python may raise during a program’s execution. Beginning with Python 1.5, all built-in exceptions are classes. Prior to 1.5, they were strings; to force string exceptions for backward compatibility, use the -X command-line option flag. Class exceptions are mostly indistinguishable from strings, unless concatenated.

Base Classes (Categories)

Exception

Root superclass for all exceptions.

StandardError

Superclass for all other built-in exceptions; a subclass of the Exception root class.

ArithmeticError

Superclass for OverflowError, ZeroDivisionError, FloatingPointError; subclass of StandardError.

LookupError

Superclass for IndexError, KeyError; subclass of StandardError.

Specific Exceptions

AssertionError

Raised when an assert statement’s test is false.

AttributeError

On attribute reference or assignment failure.

EOFError

Immediate end-of-file hit by input( ) or raw_input( ).

FloatingPointError

When a floating-point operation fails.

IOError

I/O or file-related operation failure.

ImportError

On failure of import to find module or attribute.

IndexError

On out-of-range sequence offset (fetch or assign).

KeyError

On reference to non-existent mapping key (fetch).

KeyboardInterrupt

On user entry of the interrupt key (often Ctrl-C).

MemoryError

On recoverable memory exhaustion.

NameError

On failure to find a local or global unqualified name.

OverflowError

On excessively large arithmetic operation.

RuntimeError

Obsolete catch-all; define a suitable error instead.

SyntaxError

On parser encountering ...

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