Python Functions from "30 Seconds of Code"

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#python #function

Python when function - to apply a function when predicate(x) is True 
def when(predicate, when_true):
  return lambda x: when_true(x) if predicate(x) else x
  
EXAMPLES
double_even_numbers = when(lambda x: x % 2 == 0, lambda x : x * 2)
double_even_numbers(2) # 4
double_even_numbers(1) # 1
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#python #function

Python compose function - performs right-to-left function composition 
from functools import reduce

def compose(*fns):
  return reduce(lambda f, g: lambda *args: f(g(*args)), fns)


EXAMPLES
add5 = lambda x: x + 5
multiply = lambda x, y: x * y
multiply_and_add_5 = compose(add5, multiply)

multiply_and_add_5(5, 2) # 15
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#python #lists #function

Build a list using an iterator Python unfold function 
def unfold(fn, seed):
  def fn_generator(val):
    while True: 
      val = fn(val[1])
      if val == False: break
      yield val[0]
  return [i for i in fn_generator([None, seed])]
  
  
EXAMPLES
f = lambda n: False if n > 50 else [-n, n + 10]
unfold(f, 10) # [-10, -20, -30, -40, -50]

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Python Functions from "30 Seconds of Code"

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