Tricks with Functions in Python: Object-functions, lambda, TryCatch, Currying (Partial)

Python-Functions-tricks.py

## Functions -----------

## Multiple return
def f():
    a = 5
    b = 6
    c = 7
    return a, b, c

a, b, c = f()
print(a)
print(c)

## Alternative Option
def f():
    a = 5
    b = 6
    c = 7
    return {'a' : a, 'b' : b, 'c' : c}

print(f())


## Treated functions as object
import re

def remove_punctuation(value):
    return re.sub('[!#?]', '', value)

## Put functions by name as a list
clean_ops = [str.strip, remove_punctuation, str.title]
states = ['   Alabama ', 'Georgia!', 'Georgia', 'georgia', 'FlOrIda', 
            'south   carolina##', 'West virginia?']

## Combined / Generic function
def clean_string(strings, ops):
    out = []
    for s in strings:
        for function in ops:
            s = function(s)
        out.append(s)
    return out 

clean_string(states, clean_ops)

## Use function name as a argument
list(map(remove_punctuation, states))

## Annoynymous lambda function
list(map(lambda s: remove_punctuation(str.strip(s)), states))

strings = ['foo', 'card', 'bar', 'aaaa', 'abab']
strings.sort(key=lambda x: len(set(list(x))))
print(strings)


## Currying: Partial Argument Application
'''Currying is computer science jargon (named after the mathematician Haskell Curry) 
that means deriving new functions from existing ones by partial argument application'''
def add_number(a, b):
    return a + b

add_5_to = lambda b: add_number(5, b)

add_number(2, 5)
add_5_to(2)

from functools import partial
add_5_to2 = partial(add_number, a=5)
add_5_to2(b=2)

## Try Catch ------
def attempt_float(x):
    try:
        return float(x)
    except: ## maybe only ignore some (ValueError, TypeError)
        return 'Error'
    finally: ## try block success or not run this
        print('Done anyway')

attempt_float(6)
attempt_float('hello') ## ValueError