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Beautiful Python

3e45c02f2ae5f812a55c4975124da6b2?s=47 Xuanyi
April 03, 2014

Beautiful Python

What makes python a beautiful language?

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Xuanyi

April 03, 2014
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  1. Beautiful Python SyPy  April  2014 Xuanyi  Chew

  2. pphotography-­‐‑blog.blogspot.com

  3. What is beauty? •  Tacit  knowledge •  Beauty  is  subjective(?)

    •  We  all  know  it,  but  cannot  explain  it. •  But  science  can!
  4. humanorigins.si.edu

  5. styleround.com

  6. lem-­‐‑studios.com

  7. Cosmos:  A  Space  Time  Odyssey,  FOX

  8. Beauty Is Quantifiable •  Sensible •  Simple •  Standard • 

    Smart
  9. Beautiful Python Code is: •  Sensible •  Simple •  Standard

    •  Smart
  10. CHECK FOR PALINDROME

  11. Check for Palindrome is_palindrome = lambda s: s == s[::-1]!

    !
  12. Check for Palindrome is_palindrome = lambda s: s == s[::-1]!

    ! ✔ Sensible ✔ Simple ✖ Standard ✔ Smart
  13. Check for Palindrome def is_palindrome(s):! return s == s[::-1]!

  14. WRITE A SPELL CHECK

  15. Write a Spell Check import re, collections! ! def words(text):

    return re.findall('[a-z]+', text.lower()) ! ! def train(features):! model = collections.defaultdict(lambda: 1)! for f in features:! model[f] += 1! return model! ! NWORDS = train(words(file('big.txt').read()))! ! alphabet = 'abcdefghijklmnopqrstuvwxyz'! ! def edits1(word):! splits = [(word[:i], word[i:]) for i in range(len(word) + 1)]! deletes = [a + b[1:] for a, b in splits if b]! transposes = [a + b[1] + b[0] + b[2:] for a, b in splits if len(b)>1]! replaces = [a + c + b[1:] for a, b in splits for c in alphabet if b]! inserts = [a + c + b for a, b in splits for c in alphabet]! return set(deletes + transposes + replaces + inserts)! ! def known_edits2(word):! return set(e2 for e1 in edits1(word) for e2 in edits1(e1) if e2 in NWORDS)! ! def known(words): return set(w for w in words if w in NWORDS)! ! def correct(word):! candidates = known([word]) or known(edits1(word)) or known_edits2(word) or [word]! return max(candidates, key=NWORDS.get)!
  16. Write a Spell Check import re, collections! ! def words(text):

    return re.findall('[a-z]+', text.lower()) ! ! def train(features):! model = collections.defaultdict(lambda: 1)! for f in features:! model[f] += 1! return model! ! NWORDS = train(words(file('big.txt').read()))! ! alphabet = 'abcdefghijklmnopqrstuvwxyz'! ! def edits1(word):! splits = [(word[:i], word[i:]) for i in range(len(word) + 1)]! deletes = [a + b[1:] for a, b in splits if b]! transposes = [a + b[1] + b[0] + b[2:] for a, b in splits if len(b)>1]! replaces = [a + c + b[1:] for a, b in splits for c in alphabet if b]! inserts = [a + c + b for a, b in splits for c in alphabet]! return set(deletes + transposes + replaces + inserts)! ! def known_edits2(word):! return set(e2 for e1 in edits1(word) for e2 in edits1(e1) if e2 in NWORDS)! ! def known(words): return set(w for w in words if w in NWORDS)! ! def correct(word):! candidates = known([word]) or known(edits1(word)) or known_edits2(word) or [word]! return max(candidates, key=NWORDS.get)! ✔ Sensible ✔ Simple ✔ Standard ✔ Smart
  17. A SIEVE OF ERATOSTHENES

  18. A Sieve Of Erathosthenes from itertools import compress! ! def

    vprimes(maximum=10**6):! maxidx = maximum//2! sieve = [True] * maxidx! j = 0! for i in range(1, int(maxidx**0.5)+1):! j += 4*i! if sieve[i]:! step = 2*i + 1! sieve[j::step] = [False] * -(-(maxidx-j) // step)! primes = list(compress(range(1, maximum, 2), sieve))! primes[0] = 2! return primes!
  19. A Sieve Of Erathosthenes ! def rwh_primes2(n):! correction = (n%6>1)!

    n = {0:n,1:n-1,2:n+4,3:n+3,4:n+2,5:n+1}[n%6]! sieve = [True] * (n/3)! sieve[0] = False! for i in xrange(int(n**0.5)/3+1):! if sieve[i]:! k = 3*i+1|1! sieve[((k*k)/3) ::2*k] = [False]*((n/6-(k*k)/6-1)/k+1)! sieve[(k*k+4*k-2*k*(i&1))/3::2*k] = [False]*((n/6-(k*k +4*k-2*k*(i&1))/6-1)/k+1)! return [2,3] + [3*i+1|1 for i in xrange(1,n/3-correction) if sieve[i]]! !
  20. Non-Toy Examples There  can  be  beautiful  modules  and  projects  

    too – requests  by  Kenneth  ReiT – flask  by  Armin  Ronacher – Minecraft  in  Python  by  Michael  Fogleman   (900+  lines!  Eat  this,  Notch!)
  21. How to Write Beautiful Python •  Use  correct  data  structures

    •  Write  obvious  code •  Be  clever  in  algorithm,  not  in  code •  PEP-­‐‑8  is  a  good  guide •  PEP-­‐‑20  is  a  GREAT  guide.