How to multiply in python

Short answer:

result = 3 * 2
print(result) # 6

Multiply numbers with the * operator:

The most common way to multiply 2 (or more) numbers would be using the operator (*) this is the syntax to use it:

syntax: num1*num2

Complete example:

def multiply (num1, num2):
	return num1*num2

print(multiply(3, 2)) # Output: 6

But how could we achieve this without using this operator?

Multiply numbers without the * operator:

Let´s say that you dont want to use the (*) operator. Here´s the way to do it:

def multWithout(num1, num2):
    result = 0
    for x in range(num2):
        result +=num1
    return result

print(multWithout(2,10)) # Output: 20

We created a function that receives 2 numbers, we declared a variable result and start is as "0" to store our values and we´ll loop as many times as num2. For each itaration result will be updated adding num1 to the stored ammount.

Multiply as a power operation alternative

The process would be pretty much alike, but the result variable would start as 1, since we will be multiplying instead of adding and as we all know, multiplying with "0" is not a very good idea.

def powerMult(num1, num2):
    result = 1
    for x in range(num2):
        result *= num1 
    return result

print(mult2(3, 3)) # 27

Multiply strings

Multiplying strings will follow the same structure, here´s an example:

def multString (str, num):
    return  str*num

print(multString("How to multiply in python ", 2)) # Output: How to multiply in python How to multiply in python 

The function multString recevies 2 elements, the string we want to multiply and the second element will be the ammount of times it will repeat (multiply).

Multiply lists of numbers with * operator

The way to multiply a list using the * operator will ask to loop through the given array and multiply each element storing the value on a result variable to return it.

arr = [1, 2, 3, 4, 5]

def multiplyList(list):
 
    # Multiplying one by one
    result = 1
    for x in list:
        result = result * x
    return result

print (multiplyList(arr)) # Output: 120

Multiply lists of numbers with numpy

Numpy is a library widely used by many programmers to handle complex mathematics operations. Here´s how to use it to multiply lists:

import numpy
arr = [1, 2, 3, 4, 5]

def multNumpy(arr):
    return numpy.prod(arr)

print(multNumpy(arr))
#Output: 120

First we need to import numpy to be able to use it, and then with numpy.prod() we pass the element we want to multiply (in this case, our array of numbers)

Multiply lists of numbers with reduce

Lambda is one of the most used methods in the python library, here´s how to use it along with reduce to multiply lists

from functools import reduce
arr = [1, 2, 3, 4, 5]

def MultListLambaReduce(arr):
    return reduce((lambda x, y: x * y), arr)

print(MultListLambaReduce(arr))
#Output: 120

Multiply lists of numbers with math.prod()

Using the math library you can multiply a list of numbers, here´s an example:

import math
arr = [1, 2, 3, 4, 5]

def multProd(arr):
    return math.prod(arr)

print(multProd(arr)) # Output: 120

We covered different ways to multiply in python numbers, strings and lists (arrays of numbers) with different methos, from the most simple and usual one, as simple as using the (*) operator, to more complex ones using libraries like numpy or math.

Hope you enjoyed your reading and keep on the Geek side.