chapter-10.1-exceptions.md

Errors and Exceptions

Errors that occurs during execution of code are known as exceptions. Some of common exceptions we encounter everyday are as follows:

1. SyntaxError
2. ZeroDivisionError
3. IndexError
4. KeyError
5. ValueError
6. NameError
7. TypeError

To know more about exceptions, we can see python documentation for Errors and Exceptions

SyntaxError

Syntax Error occurs when user enters invalid syntax in the code. Some of the example codes that give syntax errors are as follows:

x = 5 +     # Syntax Error occurs since + operator used without other value

y = 5 *** 5 # Syntax Error occurs since there is no operation *** in python

SyntaxError: invalid syntax

SyntaxError is also known as parsing error since if finds unexpected character or a set of characters while parsing the source code.

ZeroDivisionError

Zero division error occurs when we try to divide a number by zero. if we try to run the following code it gives us ZeroDivisionError

x = 5/0

The console should print out the following:

Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
ZeroDivisionError: division by zero

IndexError

Index Errors such as Index Out Of Range errors occur when we want to access an item from the collection data using indexes.

x = [1,2,3,4,5]
print(x[10])

While executing above line, it gives us IndexError.

Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
IndexError: list index out of range

TypeError

TypeError occurs when we try to do operations between unsupported data types.

def add(a,b):
    return a+b
print(add(5, "abc"))

While executing above line, it gives us TypeError.

Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "<stdin>", line 2, in add
TypeError: unsupported operand type(s) for +: 'int' and 'str'

There are numerous built-in exceptions in python. We can check them out in python documentation page.

https://docs.python.org/3/library/exceptions.html

Exception Hierarchy

All Exceptions inherit from the BaseException class. The Class Hierarchy for built-in exceptions is as follows:

BaseException
 +-- SystemExit
 +-- KeyboardInterrupt
 +-- GeneratorExit
 +-- Exception
      +-- StopIteration
      +-- StopAsyncIteration
      +-- ArithmeticError
      |    +-- FloatingPointError
      |    +-- OverflowError
      |    +-- ZeroDivisionError
      +-- AssertionError
      +-- AttributeError
      +-- BufferError
      +-- EOFError
      +-- ImportError
      |    +-- ModuleNotFoundError
      +-- LookupError
      |    +-- IndexError
      |    +-- KeyError
      +-- MemoryError
      +-- NameError
      |    +-- UnboundLocalError
      +-- OSError
      |    +-- BlockingIOError
      |    +-- ChildProcessError
      |    +-- ConnectionError
      |    |    +-- BrokenPipeError
      |    |    +-- ConnectionAbortedError
      |    |    +-- ConnectionRefusedError
      |    |    +-- ConnectionResetError
      |    +-- FileExistsError
      |    +-- FileNotFoundError
      |    +-- InterruptedError
      |    +-- IsADirectoryError
      |    +-- NotADirectoryError
      |    +-- PermissionError
      |    +-- ProcessLookupError
      |    +-- TimeoutError
      +-- ReferenceError
      +-- RuntimeError
      |    +-- NotImplementedError
      |    +-- RecursionError
      +-- SyntaxError
      |    +-- IndentationError
      |         +-- TabError
      +-- SystemError
      +-- TypeError
      +-- ValueError
      |    +-- UnicodeError
      |         +-- UnicodeDecodeError
      |         +-- UnicodeEncodeError
      |         +-- UnicodeTranslateError
      +-- Warning
           +-- DeprecationWarning
           +-- PendingDeprecationWarning
           +-- RuntimeWarning
           +-- SyntaxWarning
           +-- UserWarning
           +-- FutureWarning
           +-- ImportWarning
           +-- UnicodeWarning
           +-- BytesWarning
           +-- EncodingWarning
           +-- ResourceWarning