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# python has... oddities

import sys

print >>sys.stdout, 'hello world!'# hello world!

from __builtin__ import int# ... uh thanks?

from __builtin__ import True as False# uh oh...

from __future__ import braces# ... SyntaxError: not a chance

likes_art = True

# trivia: what am i?where_to_go = likes_art and 'museum' or 'nascar'

# this is another way to do it...where_to_go = ('nascar', 'museum')[bool(likes_art)]

# lazily now!where_to_go = (lambda: 'nascar', lambda: 'museum')[bool(likes_art)]()

# greanevrf - gunax tbq sbe clguba >2.5!# jure_g_tb = 'zhfrhz' vs yvxrf_neg ryfr 'anfpne'

likes_art = True

# trivia: what am i?where_to_go = likes_art and 'museum' or 'nascar'

# this is another way to do it...where_to_go = ('nascar', 'museum')[bool(likes_art)]

# lazily now!where_to_go = (lambda: 'nascar', lambda: 'museum')[bool(likes_art)]()

# ternaries - thank god for python >2.5!where_to_go = 'museum' if likes_art else 'nascar'

# str encoding

print 'hello world!'.encode('rot13')# uryyb jbeyq!

print 'hello world!'.encode('rot13').decode('rot13')# hello world!

print 'hello world!.'.encode('zlib')# x\x9c\xcbH\xcd\xc9\xc9W(\xcf/\xcaIQT(\xc9\xc8...

print 'hello world!'.encode('zlib').decode('zlib')# hello world!

# registering custom str encoding

def register_codec(name, encode=None, decode=None): import codecs if not encode: def encode(val): raise Exception(name + ' does not support encoding') if not decode: def decode(val): raise Exception(name + ' does not support decoding') def codec(searched_name): if searched_name != name: return None return codecs.CodecInfo( name=name, encode=encode, decode=decode) codecs.register(codec)

# custom "reverser" encoding

def reverser(val): return val[::-1], len(val)

register_codec('reverser', encode=reverser, decode=reverser)

print 'hello world!'.encode('reverser')# !dlrow olleh

print 'hello world!'.encode('reverser').decode('reverser')# hello world!

# custom "hail mary" decoder

def hail_mary_decode(val): import chardet result = chardet.detect(val) return val.decode(result['encoding']), len(val)

register_codec('hail_mary', decode=hail_mary_decode)

print '\xe3\x82\xab\xe3\x83\xac\xe3\x83\xb3\xe3\x83\x80'.decode('utf-8')# print '\xe3\x82\xab\xe3\x83\xac\xe3\x83\xb3\xe3\x83\x80'.decode('hail_mary')#

print '\xa5\xab\xa5\xec\xa5\xf3\xa5\xc0'.decode('euc_jp')# print '\xa5\xab\xa5\xec\xa5\xf3\xa5\xc0'.decode('hail_mary')#

# slicing / indexing / keying

print range(10)[0]# 0

print range(10)[0:5]# [0, 1, 2, 3, 4]

print range(10)[::2]# [0, 2, 4, 6, 8]

print range(10)[::-1]# [9, 8, 7, 6, 5, 4, 3, 2, 1, 0]

print dict(hello='world')['hello']# world

# deep slicing / indexing / keying

class PassThrough(object): def __getitem__(self, name): # magic method to return syntax args directly return name

pass_through = PassThrough()

print pass_through[1]# 1

print pass_through[1, 2, 3]# (1, 2, 3)

print pass_through['hello world!']# hello world!

# slicing gets weird

print pass_through[:]# slice(None, None, None)

print pass_through[...]# Ellipsis

print pass_through[..., ..., ..., ...]# (Ellipsis, Ellipsis, Ellipsis, Ellipsis)

print pass_through[..., :, ...]# (Ellipsis, slice(None, None, None), Ellipsis)

# abusing slicing

class parens_be_gone(object): # square brackets are better than parens

def __init__(self, func): self.func = func

def __getitem__(self, args): if not isinstance(args, tuple): args = (args,) return self.func(*args)

def __call__(self, *a, **kw): raise Exception('We do not like (), try []?')

# activate slice abuse

@parens_be_gonedef sum_nums(*args): return sum(args)

@parens_be_gonedef shout_it(name): return 'HELLO {}!'.format(name.upper())

print sum_nums[1, 2, 3, 4, 5]# 15

print shout_it['bryan']# HELLO WORLD!

# magic methods

class Roughly(object): def __init__(self, num): self.num = num

def __invert__(self): return '%d ± 10%' % self.num

print ~Roughly(5)# 5 ± 10%

# magic methods continued

class DoublePlus(object): def __init__(self, plusses=0): self.plusses = plusses

def __pos__(self): return DoublePlus(self.plusses + 1)

def __repr__(self): return '%d plusses' % self.plusses

print ++DoublePlus()# 2 plusses

# complementary magic methods for operators

class Man(object): def __add__(self, right_other): if right_other == 'Dog': return 'best buds' return self

def __radd__(self, left_other): if left_other == 'Dog': return 'bestest buds' return self

print Man() + 'Dog'# best buds

print 'Dog' + Man()# bestest buds

# magic methods to act like you aren't using python

class pipe(object): def __init__(self, func): self.func = func

def __ror__(self, other): return self.func(other)

def __call__(self, *a, **kw): return pipe(lambda x: self.func(x, *a, **kw))

# magic methods to act like you aren't using python continued

@pipedef _map(iterable, func): return [func(i) for i in iterable]

@pipedef _filter(iterable, func): return [i for i in iterable if func(i)]

print (range(10) | _map(lambda i: i * 3) | _filter(lambda i: i % 2 == 0) | _map(str))# ['0', '6', '12', '18', '24']

# magic methods for elegant DSLs

class RegexEquals(object): def __init__(self, regex): import re self.regex = re.compile(regex)

def __eq__(self, other): return bool(self.regex.match(other))

class TypeEquals(object): def __init__(self, *tipes): self.tipes = tipes

def __eq__(self, other): return isinstance(other, self.tipes)

# magic methods for elegant DSLs continued

URL = RegexEquals(r'(https?|ftp)://[^\s/$.?#].[^\s]*')NUM = RegexEquals(r'\d+')INT = TypeEquals(int, long)

print 'larry' == URL# False

print 'http://zapier.com/' == URL# True

print '123' == NUM# True

print {'url': 'http://zapier.com/', 'visits': 4} == {'url': URL, 'visits': INT}# True

# magic methods for abuse

class DidYouMean(object): def __getattr__(self, name): if name.startswith('__'): raise AttributeError('No magic did you mean.') from difflib import SequenceMatcher scored_attrs = [ (SequenceMatcher(None, name, attr).ratio(), attr) for attr in dir(self) if not attr.startswith('__') ] sorted_attrs = sorted([ (score, attr) for score, attr in scored_attrs if score > 0.5 ], reverse=True) best_name = next(iter(sorted_attrs), (None, None))[1] if not best_name: raise AttributeError('No "matching" `%s` attribute' % name) return getattr(self, best_name)

# activate magic methods abuse

class SomeModel(DidYouMean): first_name = 'bryan' last_name = 'helmig'

person = SomeModel()

print person.first_name# bryan

print person.furst_name# bryan

print person.address# .. AttributeError: No "matching" `address` attribute

# magic methods for evil

class specialint(int): def __add__(self, right_other): if self == 1 and right_other == 1: return 3 return super(specialint, self).__add__(right_other)

print specialint(1) + 1# 3

__builtins__.int = specialintprint int(1) + 1# 3

print 1 + 1# 2

# literals get coerced way before builtins are referenced... ¯\_( )_/¯ # https://benkurtovic.com/2015/01/28/python-object-replacement.html# http://blaag.haard.se/Using-the-AST-to-hack-constants-into-Python/

# ast / parser

import parser

tree = parser.expr('(a + 1) or {1: "test"}').tolist()print tree# [258, [327, [312, [313, [314, [315, [316, [317, [318, [7, '('] ..# [ ... [3, '"test"'], [27, '}']], [4, ''], ...]

def recurse(val): import token if isinstance(val, int): return token.tok_name.get(val, val) elif isinstance(val, list): return [recurse(v) for v in val] return val

print recurse(tree)# [258, [327, [312, [313, [314, [315, [316, [317, [318, [7, '('] ..# [ ... ['STRING', '"test"'], ['RBRACE', '}']], ['NEWLINE', ''], ...]

# ast tools can be repurposed and practical

def pyson(val): # JSON is lame. Eval is lame. import ast return ast.literal_eval(val)

print pyson('"hello world!"')# hello world!

print pyson("{1234: 'integer keys!'}")# {1234: 'integer keys!''}

print pyson('import json')# ... SyntaxError: invalid syntax

# mini lisp calc

def tokenize(program): return program.replace('(', ' ( ').replace(')', ' ) ').split()

def reshape_tokens(tokens): token = tokens.pop(0) if '(' == token: deep_tokens = [] while tokens[0] != ')': deep_tokens.append(reshape_tokens(tokens)) tokens.pop(0) return deep_tokens try: return int(token) except: return token

program = '(* 2 (+ 3 5))'print tokenize(program)# ['(', '*', '2', '(', '+', '3', '5', ')', ')']

print reshape_tokens(tokenize(program))# ['*', 2, ['+', 3, 5]]

# mini lisp calc continued

import operatorglobal_env = {'+': operator.add, '-': operator.sub, '*': operator.mul, '/': operator.div}

def evaluate(tokens, env=global_env.copy()): if isinstance(tokens, basestring) and tokens in env: return env[tokens] elif not isinstance(tokens, list): return tokens else: func = evaluate(tokens[0], env) args = [evaluate(arg, env) for arg in tokens[1:]] return func(*args)

program = '(* 2 (+ 3 5))'print evaluate(read_tokens(tokenize(program)))# 16

# http://norvig.com/lispy.html & http://norvig.com/lispy2.html