In [9]:
try:
  x= 10/0
  # code with possible error (exceptions)
except ZeroDivisionError:
  print('Divide by zero')
  x = None
  # handling error

print(x)

Divide by zero
None
In [16]:
lst = [1,2,3,4,5]
try:
  print(lst[10])
except IndexError: # handle specific exception
  print('Out of range')

lst[10]

Out of range

---------------------------------------------------------------------------
IndexError                                Traceback (most recent call last)
<ipython-input-16-1c2b54f067d2> in <cell line: 7>()
      5   print('Out of range')
      6 
----> 7 lst[10]

IndexError: list index out of range
In [13]:
try:
  num = int(input('Enter a number: '))
except ValueError: # handle specific exception
  print('Not a number')
else: # if no exception
  print(num)

Enter a number: 5
5
In [15]:
try:
  num = int(input('Enter a number: '))
except ValueError: # handle specific exception
  print('Not a number')
else: # if no exception
  print(num)
finally: # always
    print('This is always executed')

Enter a number: 5
5
This is always executed
In [19]:
x = -1

if x < 0:
  raise ValueError("Sorry, no numbers below zero")

---------------------------------------------------------------------------
ValueError                                Traceback (most recent call last)
<ipython-input-19-ce3195fd66fa> in <cell line: 3>()
      2 
      3 if x < 0:
----> 4   raise ValueError("Sorry, no numbers below zero")

ValueError: Sorry, no numbers below zero
In [18]:
x = "hello"

if not type(x) is int:
  raise TypeError("Only integers are allowed")

---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)
<ipython-input-18-bc91768a6271> in <cell line: 3>()
      2 
      3 if not type(x) is int:
----> 4   raise TypeError("Only integers are allowed")

TypeError: Only integers are allowed
In [20]:
def divide(x, y):
  # try:
  #   result = x // y
  # except ZeroDivisionError:
  #   print("Sorry ! You are dividing by zero ")
  # else:
  #   print("Yeah ! Your answer is :", result)

divide(5,0)

Sorry ! You are dividing by zero
In [22]:
def divide(x, y):
  '''This function divides two numbers
  Inputs:
      x: int
      y: int
  Output:
      result: float
  '''
  assert y != 0
  assert type(x) == int and type(y) == int, 'Wrong type'
  return x / y

divide(5,1.)

---------------------------------------------------------------------------
AssertionError                            Traceback (most recent call last)
<ipython-input-22-972854fe6427> in <cell line: 6>()
      4   return x / y
      5 
----> 6 divide(5,1.)

<ipython-input-22-972854fe6427> in divide(x, y)
      1 def divide(x, y):
      2   assert y != 0
----> 3   assert type(x) == int and type(y) == int, 'Wrong type'
      4   return x / y
      5 

AssertionError: Wrong type
In [27]:
def copy(L1,L2):
  ''' Assumes L1,L2 are lists
  Mutates L2 to be a copy of L1
  '''
  while len(L2) > 0:
    L2.pop()
  for e in L1:
    L2.append(e)

L1 = [1,2,3]
L2 = [4,5,6]
copy(L1,L2)
print(L2)
#

[None]
In [29]:
L1 = [1,2,3]
copy(L1,L1)
print(L1)

[]