Python's Functional Tools

Advanced Python Magic

Transcript

1. Functional Python Tools Advanced Python Magic
2. I’m Julian Gindi • Python developer at iStrategylabs (here) • (small-time) Python core contributor • github.com/juliangindi • @JulianGindi • JulianGindi.com • lebowski.juliangindi.com
3. Python @isl • Django (content-heavy websites) • General scripting and internal tools • Fabric (executing commands on our servers) • Salt (provisioning our servers)
4. Goals • Basic understanding of functional programming • Explain how it can help you craft simple, yet powerful code • Show you a couple practical applications of the functional paradigm
5. Golden Circle
6. Functional Programming
   (What) • First class functions. Higher-order functions • Pure functions • State • Immutable Data • Verbs instead of nouns
7. Python? • Not a functional language in a “pure” sense • Multi paradigm language • Doesn't really matter - tools are still useful and awesome • Practical
8. Why? • Downright awesome • Programs are easier to understand and debug • Often faster • Superior ability to deal with concurrency
9. How? • Time for some CODE!
10. >>> my_tuple = ('A', 'B', ‘C’) >>> len(my_tuple) 3 >>> my_tuple.append('D') Traceback (most recent call last): File "<stdin>", line 1, in <module> AttributeError: 'tuple' object has no attribute 'append'
11. Practical Features
    (Core) • Closures • Lambda’s • Iterators, generators • Partials • List Comprehension • Tuples • Built in functions (map, reduce, apply)
12. # List Comprehensions 
 def square_list(items): new_list = [] new_list.append([x * x for x in items]) return new_list ! print square_list([1,2,3]) ! >> [1, 4, 9]
13. # Closures ! def average_closure(a, b): def sum(): return a + b return sum() / 2 ! print average_closure(4, 4) ! >> 4
14. import operator ! # Lambdas ! def weird_average(func, data) : return reduce(operator.add, map(func, data)) / len(data) ! print weird_average(lambda x: x * x , [1,2,3]) ! >> 4.66
15. # Generators ! def fibonacci() : prev, current = 0,1 while True : yield current prev, current = current, prev + current ! # Generator instantiation gen = fibonacci() ! # Generator usage for i in range(10) : print gen.next() ! >> 1 1 2 3 5 8 13 21 34 55
16. # PARTIALS ! from functools import partial ! def power(x,y): return x ** y ! square = partial(power, y = 2) cube = partial(power, y = 3) ! assert (square(5), cube(7)) == (25, 343) ! ! !
17. How to get started • ‘import functools’ • Create a simple program in a functional style • http://www.defmacro.org/ ramblings/fp.html - Functional programming for the rest of us • Execution in the Kingdom of Nouns