In [1]:

    

def pascal(n):
    ''' Recursive method to print the line of Pascal's triangle. '''
    if n == 1:
        return [1]
    else:
        # return the current line wrapped in [1, ..., 1]
        curr_line = [1]
        prev_line = pascal(n - 1) # recursively find the previous line
        for i in range(len(prev_line) - 1):
            curr_line.append(prev_line[i] + prev_line[i + 1])
        curr_line.append(1)
        return curr_line


    

In [2]:

    

pascal(2)


    

    
Out[2]:





[1, 1]

In [3]:

    

pascal(3)


    

    
Out[3]:





[1, 2, 1]

In [4]:

    

pascal(4)


    

    
Out[4]:





[1, 3, 3, 1]

In [32]:

    

def pascal2(n):
    ''' Non recursive version which uses list comprehension. '''
    row = [1]
    k = [0] # this is needed to allow zip to provide the right tuple
    for x in range(max(0,n)):
        print(row) # prints the current row
        row=[l+r for l,r in zip(row+k,k+row)] # calculate the next row for use in the next iteration
#     return row # if we want to return only the last row


    

In [34]:

    

pascal2(4)


    

    




[1]
[1, 1]
[1, 2, 1]
[1, 3, 3, 1]

In [ ]: