python-sum-lambda-functions.py

# Correct way of getting sumOfIntegers
def sumOfIntegers(lb, ub):
    l = lb - 1
    return ((ub * (ub + 1)) / 2) - ((l * (l + 1)) / 2)

print(sumOfIntegers(2, 5))

# To demonstrate lambda functions we will loop through the range
# Conventional approach, we need to write different functions for
# sum of range of numbers
# sum of squares in range of numbers
# and more
def sum(lb, ub):
    total = 0
    for i in range(lb, ub + 1):
        total += i
    return total
print "sum of integers using conventional approach " + str(sum(3, 5))

def sumOfSquares(lb, ub):
    total = 0
    for i in range(lb, ub + 1):
        total += (i * i)
    return total
print "sum of squares using conventional approach " + str(sumOfSquares(3, 5))

# With lambda functions, we can get more concise and readable code
def sum(f, lb, ub):
    total = 0
    for i in range(lb, ub + 1):
        total += f(i)
    return total
print "sum of integers using lambda functions " + str(sum(lambda i: i, 3, 5))
print "sum of squares using lambda functions " + str(sum(lambda i: i * i, 3, 5))

# We can also pass named function as argument
def cube(i): return i * i * i
print "sum of cubes using lambda functions " + str(sum(lambda i: cube(i), 3, 5))