reduce function in Python3+

Oscar Eduardo Bolaños Ocampo — Tue, 12 Jan 2021 05:26:48 +0000

The reduce function is part of functools module of Python, you need two arguments for used, one a function and two a iterable. The reduce function applies the first argument to each element of iterable cumulatively. This function is equivalent to:

def reduce(function, iterable, initializer=None):
    it = iter(iterable)
    if initializer is None:
        value = next(it)
    else:
        value = initializer
    for element in it:
        value = function(value, element)
    return value

This is the Python documentation example:

from functools import reduce

output = reduce(lambda x, y: x+y, [1, 2, 3, 4, 5]) 
print(output)

[1]: 15

That is useful in some cases like in a math series:

from functools import reduce

elements = range(1, 36)
reduce(lambda x, y: x+(1/y**2), elements)

[1]: 1.616766914907197

elements = range(1, 360)
reduce(lambda x, y: x+(1/y**2), elements)

[2]: 1.642152427473518

elements = range(1, 3600)
reduce(lambda x, y: x+(1/y**2), elements)

[3]: 1.6446562504866367

It is not the best way to calculate π**2 / 6, but it is an example of how to use the reduce function.
π**2 / 6

from math import pi

pi**2/6

[1]: 1.6449340668482264

Can be useful for other applications but I love math so enjoy it! Anyway if you have doubts, comments, or corrections about I would like to receive feedback ♥️

Thanks for reading!

f-Strings print in Python 3.6+

Oscar Eduardo Bolaños Ocampo — Sat, 19 Dec 2020 19:47:18 +0000

This is an easy way to print messages in Python. This kind of string needs an "f" to activate the curly brackets in the string for the print function. Let's begin with a simple example like this:

user_name = input("Hello!\nWhat is your name?\n:")

In[1]: Oscar

print(f"OK {user_name}!\nI'm a computer :)")

Out[1]: OK Oscar!
        I'm a computer :)

We can use other ways to declare a string with the same result:

value = 3.14159
print(f'{value}')
print(f"pi = {value}")
print(f"""The Pi constant:
this is an approximation: {value}""")

We must be careful with the variable inside of the curly brackets because if doesn't exist a SyntaxError will pop up from python, ok that's all also you can use multiples values in a single f-string.

def plus_one(value: int) -> int:
    """sum 1 to input
       input: a number
       output: number + 1"""
    return value + 1


user_name = input("Hello!\nWhat is your name?\n:")
try:
    number = '2'
    ans = plus_one(number)

except Exception as err:
    print(f""">>> Message:
plus_one function doesn't work with {number} like input.
Here is the error honey:
{err}""")

else:
    print(f"Ok {user_name}, {number} plus_one is {ans}.")

finally:
    print("Bye!")

Thanks for reading!

DEV Community: Oscar Eduardo Bolaños Ocampo

reduce function in Python3+

f-Strings print in Python 3.6+