Python - functional programming - len(), sum(), avg() (Stackoverflow)

#!/usr/bin/env python3.13

# date: 2025.07.10

# [python - How to programm a function yielding average value of a list of values using functional style exclusively and preferably notable sophisticated? - Stack Overflow](https://stackoverflow.com/questions/79697123/how-to-programm-a-function-yielding-average-value-of-a-list-of-values-using-func)

# ---

# Coconut is a functional programming language that compiles to Python: https://coconut-lang.org/

# ---

data = [1, 4, 3, 5, 7]

print('len:', len(data))
print('sum:', sum(data))
print('avg:', sum(data)/len(data))

# -- functional ---

def f_len(data):
    match data:
        case ():
            return 0
        case (head, *tail):
            return 1 + f_len(tail)

def f_sum(data):
    match data:
        case ():
            return 0
        case (head, *tail):
            return head + f_sum(tail)

def f_avg(data):
    return f_sum(data)/f_len(data)

print('f_len:', f_len(data))
print('f_sum:', f_sum(data))
print('f_avg:', f_avg(data))

# ---

# it uses previous `f_len()`

def f_avg_2(data):
    return f_div_sum(data, f_len(data))

#def f_div_sum(data, num):
#    return f_sum(data)/num

def f_div_sum(data, num):
    match data:
        case ():
            return 0
        case (head, *tail):
            return head/num + f_div_sum(tail, num)

print('f_avg_2:', f_avg_2(data))

print('sum/len:', f_div_sum(data, f_len(data)))
print('sum/2  :', f_div_sum(data, 2))
print('sum/3  :', f_div_sum(data, 3))
print('sum/4  :', f_div_sum(data, 4))