#!/usr/bin/env python
# coding: utf-8

# ### Swapping variable values
# 
# Suppose

# In[1]:


a, b = 42, 43


# We've see the following options for swapping their values. One is using multiple assignment:

# In[2]:


a, b = b, a


# Another is using a temporary variable:

# In[3]:


temp = b
b = a
a = temp


# Here is how we can swap the values of two integer variables without using either of those tricks:

# In[4]:


a, b = 42, 43

#Suppose a == a', b = b'. That is, a' is the "old" value of a, and b' is the "old" value of b

a = a + b  #a == a' + b', b == b'
b = a - b  #a == a' + b', b == a'
a = a - b  #a == b', b == a'