Multiplying a tuple by a scalar

Question

I have the following code:

print(img.size)
print(10 * img.size)

This will print:

(70, 70)
(70, 70, 70, 70, 70, 70, 70, 70,          


        

Answer 1

adding nothing but variety..

import operator
img_size = (70, 70)
map(operator.mul, img_size, len(img_size)*(10,))

Answer 2

If you have this problem more often and with larger tuples or lists then you might want to use the numpy library, which allows you to do all kinds of mathematical operations on arrays. However, in this simple situation this would be complete overkill.

Answer 3

You can try something like this:

print [10 * s for s in img.size]

It will give you a new list with all the elements you have in the tuple multiplied by 10

Answer 4

In line with the previous answers but using numpy:

import numpy as np
result = tuple(10*np.array(img.size))

Answer 5

Just to overview

import timeit

# tuple element wise operations multiplication

# native
map_lambda = """
a = tuple(range(10000))
b = tuple(map(lambda x: x * 2, a))
"""

# native
tuple_comprehension = """
a = tuple(range(10000))
b = tuple(x * 2 for x in a)
"""

# numpy
using_numpy = """
import numpy as np
a = tuple(range(10000))
b = tuple((np.array(a) * 2).tolist())
"""

print('map_lambda =', timeit.timeit(map_lambda, number=1000))
print('tuple_comprehension =', timeit.timeit(tuple_comprehension, number=1000))
print('using_numpy =', timeit.timeit(using_numpy, number=1000))

Timings on my machine

map_lambda = 1.541315148000649
tuple_comprehension = 1.0838452139996662
using_numpy = 1.2488984129995515

Answer 6

The pythonic way would be using a list comprehension:

y = tuple([z * 10 for z in img.size])

Another way could be:

y = tuple(map((10).__mul__, img.size))