Random string generation with upper case letters and digits

Question

I want to generate a string of size N   It should be made up of numbers and uppercase English letters such as    6U1S75 4Z4UKK U911K4   How can I achieve this in a pythonic way

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I d do it this way   import random from string import digits  ascii uppercase  legals   digits   ascii uppercase  def rand string length  char set legals        output          for   in range length   output    random choice char set      return output   Or just   def rand string length  char set legals        return    join  random choice char set  for   in range length

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Generate random 16-byte ID containig letters  digits      and  -   os urandom 16  translate  f  string ascii letters  string digits -   4  encode  ascii

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import random q 2 o 1 list    r a   b   c   d   e   f   g   h   i   j   k   l   m   n   o   p   q   r   s   t   u   v   w   s   0   1   2   3   4   5   6   7   8   9   0   while q gt o       print          for i in range 1 128           x random choice list          print x end       Here length of string can be changed in for loop i e for i in range 1 length   It is simple algorithm which is easy to understand  it uses list so you can discard characters that you do not need

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Simply use Python s builtin uuid   If UUIDs are okay for your purposes  use the built-in uuid package   One Line Solution   import uuid  uuid uuid4   hex upper   0 6   In Depth Version   Example   import uuid uuid uuid4    uuid4   gt  full random uuid   Outputs something like  UUID  0172fc9a-1dac-4414-b88d-6b9a6feb91ea     If you need exactly your format  for example   6U1S75    you can do it like this   import uuid  def my random string string length 10          Returns a random string of length string length         random   str uuid uuid4      Convert UUID format to a Python string      random   random upper     Make all characters uppercase      random   random replace  -        Remove the UUID  -       return random 0 string length    Return the random string   print my random string 6     For example  D9E50C

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None of the answers so far guarantee presence of certain categories of characters like upper  lower  digits etc  so other answers may result in passwords that do not have digits  etc  Surprised that such a function is not part of standard lib  Here is what I use  def random password    nchars   7  min nupper   3  ndigits   3  nspecial   3  special string punctuation       letters   random choices string ascii lowercase  k nchars      letters upper   random choices string ascii uppercase  k min nupper      digits   random choices string digits  k ndigits      specials   random choices special  k nspecial       password chars   letters   letters upper   digits   specials     random shuffle password chars       return    join password chars

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From Python 3 6 on you should use the secrets module if you need it to be cryptographically secure instead of the random module  otherwise this answer is identical to the one of  Ignacio Vazquez-Abrams    from secrets import choice import string     join  choice string ascii uppercase   string digits  for   in range N      One additional note  a list-comprehension is faster in the case of str join than using a generator expression

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This Stack Overflow quesion is the current top Google result for  random string Python   The current top answer is      join random choice string ascii uppercase   string digits  for   in range N     This is an excellent method  but the PRNG in random is not cryptographically secure  I assume many people researching this question will want to generate random strings for encryption or passwords  You can do this securely by making a small change in the above code      join random SystemRandom   choice string ascii uppercase   string digits  for   in range N     Using random SystemRandom   instead of just random uses  dev urandom on  nix machines and CryptGenRandom   in Windows   These are cryptographically secure PRNGs  Using random choice instead of random SystemRandom   choice in an application that requires a secure PRNG could be potentially devastating  and given the popularity of this question  I bet that mistake has been made many times already   If you re using python3 6 or above  you can use the new secrets module as mentioned in MSeifert s answer      join secrets choice string ascii uppercase   string digits  for   in range N     The module docs also discuss convenient ways to generate secure tokens and best practices

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this is a take on Anurag Uniyal  s response and something that i was working on myself   import random import string  oneFile   open   Numbers txt    w   userInput   0 key count   0 value count   0 chars   string ascii uppercase   string digits   string punctuation  for userInput in range int input  How many 12 digit keys do you want           while key count  lt   userInput          key count    1         number   random randint 1  999          key   number          text   str key           str    join random sample chars 6  12            oneFile write text     n   oneFile close

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1  This will give you all caps and numbers   import string  random passkey    for x in range 8       if random choice  1 2      1          passkey    passkey join random choice string ascii uppercase       else          passkey    passkey join random choice string digits   print passkey     2  If you later want to include lowercase letters in your key  then this will also work   import string  random passkey    for x in range 8       if random choice  1 2      1          passkey    passkey join random choice string ascii letters       else          passkey    passkey join random choice string digits   print passkey

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gt  gt  gt  import string   gt  gt  gt  import random   the following logic still generates 6 character random sample    gt  gt  gt  print    join random sample  string ascii uppercase string digits  6   JT7K3Q   No need to multiply by 6   gt  gt  gt  print    join random sample  string ascii uppercase string digits  6 6    TK82HK

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Answer in one line      join random choice string ascii uppercase   string digits  for   in range N     or even shorter starting with Python 3 6 using random choices        join random choices string ascii uppercase   string digits  k N     A cryptographically more secure version  see https   stackoverflow com a 23728630 2213647      join random SystemRandom   choice string ascii uppercase   string digits  for   in range N     In details  with a clean function for further reuse    gt  gt  gt  import string  gt  gt  gt  import random  gt  gt  gt  def id generator size 6  chars string ascii uppercase   string digits          return    join random choice chars  for   in range size        gt  gt  gt  id generator    G5G74W   gt  gt  gt  id generator 3   6793YUIO    Y3U    How does it work    We import string  a module that contains sequences of common ASCII characters  and random  a module that deals with random generation   string ascii uppercase   string digits just concatenates the list of characters representing uppercase ASCII chars and digits    gt  gt  gt  string ascii uppercase  ABCDEFGHIJKLMNOPQRSTUVWXYZ   gt  gt  gt  string digits  0123456789   gt  gt  gt  string ascii uppercase   string digits  ABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789    Then we use a list comprehension to create a list of  n  elements    gt  gt  gt  range 4    range create a list of  n  numbers  0  1  2  3   gt  gt  gt    elem  for   in range 4     we use range to create 4 times  elem    elem    elem    elem    elem     In the example above  we use   to create the list  but we don t in the id generator function so Python doesn t create the list in memory  but generates the elements on the fly  one by one  more about this here    Instead of asking to create  n  times the string elem  we will ask Python to create  n  times a random character  picked from a sequence of characters    gt  gt  gt  random choice  abcde    a   gt  gt  gt  random choice  abcde    d   gt  gt  gt  random choice  abcde    b    Therefore random choice chars  for   in range size  really is creating a sequence of size characters  Characters that are randomly picked from chars    gt  gt  gt   random choice  abcde   for   in range 3     a    b    b    gt  gt  gt   random choice  abcde   for   in range 3     e    b    e    gt  gt  gt   random choice  abcde   for   in range 3     d    a    c     Then we just join them with an empty string so the sequence becomes a string    gt  gt  gt     join   a    b    b     abb   gt  gt  gt   random choice  abcde   for   in range 3     d    c    b    gt  gt  gt     join random choice  abcde   for   in range 3    dac

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import uuid lowercase str   uuid uuid4   hex     lowercase str is a random value like  cea8b32e00934aaea8c005a35d85a5c0   uppercase str   lowercase str upper     uppercase str is  CEA8B32E00934AAEA8C005A35D85A5C0

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A faster  easier and more flexible way to do this is to use the strgen module  pip install StringGenerator    Generate a 6-character random string with upper case letters and digits    gt  gt  gt  from strgen import StringGenerator as SG  gt  gt  gt  SG    u d  6    render   u YZI2CI    Get a unique list    gt  gt  gt  SG    l d  10    render list 5 unique True   u xqqtmi1pOk   u zmkWdUr63O   u PGaGcPHrX2   u 6RZiUbkk2i   u j9eIeeWgEF     Guarantee one  special  character in the string    gt  gt  gt  SG    l d  10  amp   p    render   u jaYI0bcPG 0    A random HTML color    gt  gt  gt  SG     h  6    render   u  CEdFCa    etc    We need to be aware that this      join random choice string ascii uppercase   string digits  for   in range N     might not have a digit  or uppercase character  in it   strgen is faster in developer-time than any of the above solutions  The solution from Ignacio is the fastest run-time performing and is the right answer using the Python Standard Library  But you will hardly ever use it in that form  You will want to use SystemRandom  or fallback if not available   make sure required character sets are represented  use unicode  or not   make sure successive invocations produce a unique string  use a subset of one of the string module character classes  etc  This all requires lots more code than in the answers provided  The various attempts to generalize a solution all have limitations that strgen solves with greater brevity and expressive power using a simple template language   It s on PyPI   pip install StringGenerator   Disclosure  I m the author of the strgen module

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A simple one   import string import random character   string lowercase   string uppercase   string digits   string punctuation char len   len character    you can specify your password length here pass len   random randint 10 20  password      for x in range pass len       password   password   character random randint 0 char len-1   print password

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Based on another Stack nbsp Overflow answer  Most lightweight way to create a random string and a random hexadecimal number  a better version than the accepted answer would be      06x    random randrange 16  6   upper     much faster

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I found this to be simpler and cleaner   str Key                str FullKey             str CharacterPool    01234ABCDEFfghij  gt     for int I in range 64        str Key   random choice str CharacterPool       str FullKey   str FullKey   str Key    Just change the 64 to vary the length  vary the CharacterPool to do alpha only alpha numeric or numeric only or strange characters or whatever you want

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import string from random import   characters   string ascii letters   string punctuation    string digits password       join choice characters  for x in range randint 8  16    print password

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I have gone though almost all of the answers but none of them looks easier  I would suggest you to try the passgen library which is generally used to create random passwords   You can generate random strings of your choice of length  punctuation  digits  letters and case   Here s the code for your case   from passgen import passgen string length   int input    random string   passgen length string length  punctuation False  digits True  letters True  case  upper

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Use Numpy s random choice   function  import numpy as np import string          if   name         main         length   16     a   np random choice list string ascii uppercase   string digits   length                      print    join a     Documentation is here http   docs scipy org doc numpy-1 10 0 reference generated numpy random choice html

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I was looking at the different answers and took time to read the documentation of secrets  The secrets module is used for generating cryptographically strong random numbers suitable for managing data such as passwords  account authentication  security tokens  and related secrets  In particularly  secrets should be used in preference to the default pseudo-random number generator in the random module  which is designed for modelling and simulation  not security or cryptography   Looking more into what it has to offer I found a very handy function if you want to mimic an ID like Google Drive IDs   secrets token urlsafe  nbytes None   Return a random URL-safe text string  containing nbytes random bytes  The text is Base64 encoded  so on average each byte results in approximately 1 3 characters  If nbytes is None or not supplied  a reasonable default is used   Use it the following way  import secrets import math  def id generator        id   secrets token urlsafe math floor 32   1 3       return id  print id generator     Output a 32 characters length id  joXR8dYbBDAHpVs5ci6iD-oIgPhkeQFk  I know this is slightly different from the OP s question but I expect that it would still be helpful to many who were looking for the same use-case that I was looking for

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For those of you who enjoy functional python   from itertools import imap  starmap  islice  repeat from functools import partial from string import letters  digits  join from random import choice  join chars   partial join  sep     identity   lambda o  o  def irand seqs symbols join chars  letters  digits    length 6  join join chars  select choice  breakup islice           Generates an indefinite sequence of joined random symbols each of a specific length      param symbols  symbols to select           defaults to string letters   string digits  digits 0 - 9  lower and upper case English letters        param length  the length of each sequence           defaults to 6       param join  method used to join selected symbol            defaults to    join generating a string        param select  method used to select a random element from the giving population            defaults to random choice  which selects a single element randomly       return  indefinite iterator generating random sequences of giving   param length       gt  gt  gt  from tools import irand seqs      gt  gt  gt  strings   irand seqs        gt  gt  gt  a   next strings       gt  gt  gt  assert isinstance a   str  unicode        gt  gt  gt  assert len a     6      gt  gt  gt  assert next strings     next strings              return imap join  starmap breakup  repeat  imap select  repeat symbols    None  length       It generates an indefinite  infinite  iterator  of joined random sequences  by first generating an indefinite sequence of randomly selected symbol from the giving pool  then breaking this sequence into length parts which is then joined  it should work with any sequence that supports getitem  by default it simply generates a random sequence of alpha numeric letters  though you can easily modify to generate other things   for example to generate random tuples of digits    gt  gt  gt  irand tuples   irand seqs xrange 10   join tuple   gt  gt  gt  next irand tuples   0  5  5  7  2  8   gt  gt  gt  next irand tuples   3  2  2  0  3  1    if you don t want to use next for generation you can simply make it callable    gt  gt  gt  irand tuples   irand seqs xrange 10   join tuple   gt  gt  gt  make rand tuples   partial next  irand tuples    gt  gt  gt  make rand tuples    1  6  2  8  1  9    if you want to generate the sequence on the fly simply set join to identity    gt  gt  gt  irand tuples   irand seqs xrange 10   join identity   gt  gt  gt  selections   next irand tuples   gt  gt  gt  next selections  8  gt  gt  gt  list selections   6  3  8  2  2    As others have mentioned if you need more security then set the appropriate select function    gt  gt  gt  from random import SystemRandom  gt  gt  gt  rand strs   irand seqs select SystemRandom   choice   QsaDxQ    the default selector is choice which may select the same symbol multiple times for each chunk  if instead you d want the same member selected at most once for each chunk then  one possible usage    gt  gt  gt  from random import sample  gt  gt  gt  irand samples   irand seqs xrange 10   length 1  join next  select lambda pool  sample pool  6    gt  gt  gt  next irand samples   0  9  2  3  1  6    we use sample as our selector  to do the complete selection  so the chunks are actually length 1  and to join we simply call next which fetches the next completely generated chunk  granted this example seems a bit cumbersome and it is

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I would like to suggest you next option   import crypt n   10 crypt crypt  any sring   replace          replace          upper   -n -1    Paranoic mode   import uuid import crypt n   10 crypt crypt str uuid uuid4     replace          replace          upper   -n -1

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Sometimes 0  zero   amp  O  letter O  can be confusing  So I use   import uuid uuid uuid4   hex  6  upper   replace  0   X   replace  O   Y

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I thought no one had answered this yet lol  But hey  here s my own go at it   import random  def random alphanumeric limit        ascii alphabet of all alphanumerals     r    range 48  58    range 65  91    range 97  123       random shuffle r      return reduce lambda i  s  i   chr s   r  random randint 0  len r

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Two methods    import random  math     def randStr 1 chars str  length int  - gt  str      chars    math ceil length   len chars       chars   letters 0 length      chars   list chars      random shuffle characters       return    join chars      def randStr 2 chars str  length int  - gt  str      return    join random choice chars  for i in range chars          Benchmark     from timeit import timeit  setup       import os  subprocess  time  string  random  math  def randStr 1 letters str  length int  - gt  str      letters    math ceil length   len letters       letters   letters 0 length      letters   list letters      random shuffle letters      return    join letters   def randStr 2 letters str  length int  - gt  str      return    join random choice letters  for i in range length        print  Method 1 vs Method 2      run 10 times each     for length in  100 1000 10000 50000 100000 500000 1000000       print length   characters         eff1   timeit  randStr 1 string ascii letters       format length   setup setup  number 10      eff2   timeit  randStr 2 string ascii letters       format length   setup setup  number 10      print   t  s     s  format round eff1  6   round eff2  6        print   tratio           n  format eff1 eff1  round eff2 eff1  2      Output    Method 1 vs Method 2   run 10 times each   100 characters      0 001411s   0 00179s     ratio   1 0   1 27  1000 characters      0 013857s   0 017603s     ratio   1 0   1 27  10000 characters      0 13426s   0 151169s     ratio   1 0   1 13  50000 characters      0 709403s   0 855136s     ratio   1 0   1 21  100000 characters      1 360735s   1 674584s     ratio   1 0   1 23  500000 characters      6 754923s   7 160508s     ratio   1 0   1 06  1000000 characters      11 232965s   14 223914s     ratio   1 0   1 27   The performance of first method is better

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A simpler  faster but slightly less random way is to use random sample instead of choosing each letter separately  If n-repetitions are allowed  enlarge your random basis by n times e g   import random import string  char set   string ascii uppercase   string digits print    join random sample char set 6  6     Note  random sample prevents character reuse  multiplying the size of the character set makes multiple repetitions possible  but they are still less likely then they are in a pure random choice  If we go for a string of length 6  and we pick  X  as the first character  in the choice example  the odds of getting  X  for the second character are the same as the odds of getting  X  as the first character  In the random sample implementation  the odds of getting  X  as any subsequent character are only 6 7 the chance of getting it as the first character

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If you want an easy-to-use but highly customisable key generator  use key-generator pypi package   Here is the GitHub repo where you can find the complete documentation   You can customise it to give a string jist like you want with many more options  Here s an example  from key generator key generator import generate  custom key   generate 2    -         3  10  type of value    char   capital    mix   seed   17  get key   print custom key     ZLFdHXIUe-ekwJCu  Hope this helps    Disclaimer  This uses the key-generator library which I made

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If you need a random string rather than a pseudo random one  you should use os urandom as the source  from os import urandom from itertools import islice  imap  repeat import string  def rand string length 5       chars   set string ascii uppercase   string digits      char gen    c for c in imap urandom  repeat 1   if c in chars      return    join islice char gen  None  length

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gt  gt  gt  import random  gt  gt  gt  str       gt  gt  gt  chars    abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890   gt  gt  gt  num   int raw input  How long do you want the string to be       How long do you want the string to be   10  gt  gt  gt  for k in range 1  num 1          str append random choice chars        gt  gt  gt  str      join str   gt  gt  gt  str  tm2JUQ04CK    The random choice function picks a random entry in a list  You also create a list so that you can append the character in the for statement  At the end str is   t    m    2    J    U    Q    0    4    C    K    but the str      join str  takes care of that  leaving you with  tm2JUQ04CK    Hope this helps

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you can now use a new library  python  gt   3 6  chancepy here from chancepy import Chance  random string   Chance string length 10  pool  quot someLettersAndNumbers123 quot

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This method is slightly faster  and slightly more annoying  than the random choice   method Ignacio posted   It takes advantage of the nature of pseudo-random algorithms  and banks on bitwise and and shift being faster than generating a new random number for each character     must be length 32 -- 5 bits -- the question didn t specify using the full set   of uppercase letters     ALPHABET    ABCDEFGHJKLMNPQRSTUVWXYZ23456789   def generate with randbits size 32       def chop x           while x              yield x  amp  31             x   x  gt  gt  5     return     join  ALPHABET x  for x in chop random getrandbits size   5    ljust size   A        create a generator that takes out 5 bit numbers at a time 0  31 until none left     join   the results of the generator on a random number with the right bits  With Timeit  for 32-character strings  the timing was      generate with random choice   28 92901611328125      generate with randbits   20 0293550491333        but for 64 character strings  randbits loses out     I would probably never use this approach in production code unless I really disliked my co-workers   edit  updated to suit the question  uppercase and digits only   and use bitwise operators  amp  and    instead of   and

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import string  random lower   string ascii lowercase upper   string ascii uppercase digits   string digits special            amp           def rand pass l 4  u 4  d 4  s 4       p           p append random choice lower   for x in range l        p append random choice upper   for x in range u        p append random choice digits   for x in range d        p append random choice special   for x in range s       random shuffle p      return    join p   print rand pass       5U  A4yIZvnp 51

[python] Random string generation with upper case letters and digits

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