How to sort list of tuple according to first value in tuple

# Python program to sort a list of 
# tuples by the second Item using sort()  
  
# Function to sort hte list by first item of tuple 
def Sort_Tuple(tup):  
  
    # reverse = None (Sorts in Ascending order)  
    # key is set to sort using second element of  
    # sublist lambda has been used  
    tup.sort(key = lambda x: x[0])  
    return tup  
  
# Driver Code  
tup = [(10,'rishav'), (5, 'akash'), (20 , 'ram'), (15 , 'gaurav')]  
  
# printing the sorted list of tuples 
print(Sort_Tuple(tup))