Short rot13 function - Python

Question

I am searching for a short and cool rot13 function in Python  -  I ve written this function   def rot13 s       chars    abcdefghijklmnopqrstuvwxyz      trans   chars 13   chars  13      rot char   lambda c  trans chars find c   if chars find c  gt -1 else c     return    join  rot char c  for c in s      Can anyone make it better  E g supporting uppercase characters

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Interesting exercise  -  i think i have the best solution because     no modules needed  uses only built-in functions --  no deprecation it can be used as a one liner based on ascii  no mapping dicts strings etc    Python 2  amp  3  probably Python 1    def rot13 s       return    join  chr ord n     13 if  Z   lt  n  lt   n  or n  lt   N  else -13   if n isalpha   else n for n in s    def rot13 verbose s       x          for n in s          if n isalpha                   n  is the 14th character in the alphabet so if a character is bigger we can subtract 13 to get rot13             ort   13 if  Z   lt  n  lt   n  or n  lt   N  else -13             x append chr ord n    ort           else              x append n      return    join x       crazy  min version  99 characters  disclaimer  not pep8 compatible   def r s  return   join  chr ord n   13if Z  lt n lt  n or N  gt n else-13  if n isalpha  else n for n in s

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You can also use this also  def n3bu1A n       o        key             a   n    b   o    c   p    d   q    e   r    f   s    g   t    h   u            i   v    j   w    k   x    l   y    m   z    n   a    o   b    p   c            q   d    r   e    s   f    t   g    u   h    v   i    w   j    x   k           y   l    z   m    A   N    B   O    C   P    D   Q    E   R    F   S            G   T    H   U    I   V    J   W    K   X    L   Y    M   Z    N   A            O   B    P   C    Q   D    R   E    S   F    T   G    U   H    V   I            W   J    X   K    Y   L    Z   M       for x in n          v   x in key keys           if v    True              o     key x              else              o    x     return o  Yes   n3bu1A  N zhpu fvzcyre jnl gb fnl Guvf vf zl Zragbe     print Yes

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from string import maketrans  lowercase  uppercase  def rot13 message      lower   maketrans lowercase  lowercase 13     lowercase  13      upper   maketrans uppercase  uppercase 13     uppercase  13      return message translate lower  translate upper

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Short solution   def rot13 text       return    join  x if ord x  not in range 65  91  range 97  123  else             chr   ord x -97 13  26  97  if x islower   else             chr   ord x -65 13  26  65  for x in text

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As of Python 3 1  string translate and string maketrans no longer exist  However  these methods can be used with bytes instead   Thus  an up-to-date solution directly inspired from Paul Rubel s one  is   rot13   bytes maketrans      b abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ       b nopqrstuvwxyzabcdefghijklmNOPQRSTUVWXYZABCDEFGHIJKLM   b Hello world   translate rot13    Conversion from string to bytes and vice-versa can be done with the encode and decode built-in functions

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Try this   import codecs codecs encode  text to be rot13   ed    rot 13

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Here s a maketrans translate solution  import string rot13   string maketrans        ABCDEFGHIJKLMabcdefghijklmNOPQRSTUVWXYZnopqrstuvwxyz         NOPQRSTUVWXYZnopqrstuvwxyzABCDEFGHIJKLMabcdefghijklm   string translate  Hello World    rot13     Uryyb Jbeyq

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It s very simple    gt  gt  gt  import codecs  gt  gt  gt  codecs encode  foobar    rot 13    sbbone

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For arbitrary values  something like this works for 2 x  from string import ascii uppercase as uc  ascii lowercase as lc  maketrans                                                                                                              rotate   13   ROT13                                                                     rot      join   x  rotate    -1    x rotate     -1     -1  for x in  uc lc        def rot func text  encode True                                                       ascii   uc   lc                                                                  src  trg    ascii  rot  if encode else  rot  ascii                               trans   maketrans src  trg                                                       return text translate trans                                                   text    Text to ROT    format rotate                                             encode   rot func text                                                           decode   rot func encode  False

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From the builtin module this py  import this   s    quot foobar quot   d      for c in  65  97       for i in range 26           d chr i c     chr  i 13    26   c   print  quot  quot  join  d get c  c  for c in s       sbbone

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I couldn t leave this question here with out a single statement using the modulo operator   def rot13 s       return    join  chr x islower   and   ord x  - 84    26    97                         or x isupper   and   ord x  - 52    26    65                         or ord x                       for x in s     This is not pythonic nor good practice  but it works    gt  gt  rot13  Hello World    Uryyb Jbeyq

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The following function rot s  n  encodes a string s with ROT-n encoding for any integer n  with n defaulting to 13  Both upper- and lowercase letters are supported  Values of n over 26 or negative values are handled appropriately  e g   shifting by 27 positions is equal to shifting by one position  Decoding is done with invrot s  n    import string  def rot s  n 13          Encode string s with ROT-n  i e   by shifting all letters n positions      When n is not supplied  ROT-13 encoding is assumed              upper   string ascii uppercase     lower   string ascii lowercase     upper start   ord upper 0       lower start   ord lower 0       out          for letter in s          if letter in upper              out    chr upper start    ord letter  - upper start   n    26          elif letter in lower              out    chr lower start    ord letter  - lower start   n    26          else              out    letter     return out   def invrot s  n 13          Decode a string s encoded with ROT-n-encoding     When n is not supplied  ROT-13 is assumed              return rot s  -n

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This works for uppercase and lowercase  I don t know how elegant you deem it to be    def rot13 s       rot lambda x chr ord x  13  if chr ord x lower    13  isalpha    True else chr ord x -13      s  rot i  for i in filter lambda x x      map str s        return    join s

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You can support uppercase letters on the original code posted by Mr  Walter by alternating the upper case and lower case letters    chars    AaBbCcDdEeFfGgHhIiJjKkLlMmNnOoPpQqRrSsTtUuVvWwXxYyZz    If you notice the index of the uppercase letters are all even numbers while the index of the lower case letters are odd      A   0  a   1   B   2  b   3   C   4  c   4        This odd-even pattern allows us to safely add the amount needed without having to worry about the case     trans   chars 26     chars  26    The reason you add 26 is because the string has doubled in letters due to the upper case letters  However  the shift is still 13 spaces on the alphabet    The full code    def rot13 s       chars    AaBbCcDdEeFfGgHhIiJjKkLlMmNnOoPpQqRrSsTtUuVvWwXxYyZz      trans   chars 26   chars  26      rot char   lambda c  trans chars find c   if chars find c   gt  -1 else c     return    join rot char c  for c in s    OUTPUT  Tested with python 2 7    print rot13  Hello World    -- gt  Uryyb Jbeyq

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This works on Python 2  but not Python 3     gt  gt  gt   foobar  encode  rot13    sbbone

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I found this post when I started wondering about the easiest way to implement rot13 into Python myself   My goals were    Works in both Python 2 7 6 and 3 3  Handle both upper and lower case  Not use any external libraries    This meets all three of those requirements   That being said  I m sure it s not winning any code golf competitions   def rot13 string       CLEAR    ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz      ROT13    NOPQRSTUVWXYZABCDEFGHIJKLMnopqrstuvwxyzabcdefghijklm      TABLE    x  y for x  y in zip CLEAR  ROT13        return    join map lambda x  TABLE get x  x   string      if   name         main         CLEAR    Hello  World       R13    Uryyb  Jbeyq        r13   rot13 CLEAR      assert r13    R13      clear   rot13 r13      assert clear    CLEAR   This works by creating a lookup table and simply returning the original character for any character not found in the lookup table   Update  I got to worrying about someone wanting to use this to encrypt an arbitrarily-large file  say  a few gigabytes of text    I don t know why they d want to do this  but what if they did   So I rewrote it as a generator   Again  this has been tested in both Python 2 7 6 and 3 3   def rot13 clear       CLEAR    ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz      ROT13    NOPQRSTUVWXYZABCDEFGHIJKLMnopqrstuvwxyzabcdefghijklm      TABLE    x  y for x  y in zip CLEAR  ROT13        for c in clear          yield TABLE get c  c     if   name         main         CLEAR    Hello  World       R13    Uryyb  Jbeyq        r13      join rot13 CLEAR       assert r13    R13      clear      join rot13 r13       assert clear    CLEAR

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In python-3 the str-codec that  amber mentioned has moved to codecs standard-library    gt  import codecs  gt  codecs encode  foo    rot13   sbb

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A one-liner to rot13 a string S   S translate  a   a    lambda x  1 if x gt  0 else -1  77 - a    13 for a in range 65  91

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def rot13 s       lower chars      join chr c  for c in range  97 123    ASCII a-z     upper chars      join chr c  for c in range  65 91    ASCII A-Z     lower encode   lower chars 13     lower chars  13   shift 13 bytes     upper encode   upper chars 13     upper chars  13   shift 13 bytes     output       outputstring     for c in s          if c in lower chars                  output   output   lower encode lower chars find c           elif c in upper chars              output   output   upper encode upper chars find c           else              output   output   c     return output   Another solution with shifting  Maybe this code helps other people to understand rot13 better  Haven t tested it completely

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The maketrans and translate methods of str are handy for this type of thing  Here s a general solution  import string  def make rot n n       lc   string ascii lowercase     uc   string ascii uppercase     trans   str maketrans lc   uc                            lc n     lc  n    uc n     uc  n       return lambda s  str translate s  trans   rot13   make rot n 13   rot13  foobar      sbbone

[python] Short rot13 function - Python

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