Reputation: 64853
How do I generate a string of size N, made of numbers and uppercase English letters such as:
Upvotes: 1795
Views: 1491738
Reputation: 88837
A better approach which can be considered 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
Upvotes: 61
Reputation: 3187
Use this code to quickly generate a string of repeated random text values:
import string
import random
def id_generator(size=6, chars=string.ascii_uppercase + string.digits):
return ''.join(random.choice(chars) for _ in range(size))
moja_lista = []
for a in range(20):
moja_lista.append(id_generator(3, "3etrY"))
You get 20 repeated random text values. The generator generates three-component elements from the set "3etrY" set. Everything can be set as you like.
print(len(moja_lista))
moja_lista
Upvotes: 0
Reputation: 300
A random generator function without duplicates using a set
to store values which have been generated before. Note this will cost some memory with very large strings or amounts and it probably will slow down a bit. The generator
will stop at a given amount or when the maximum possible combinations are reached.
Code:
#!/usr/bin/env python
from typing import Generator
from random import SystemRandom as RND
from string import ascii_uppercase, digits
def string_generator(size: int = 1, amount: int = 1) -> Generator[str, None, None]:
"""
Return x random strings of a fixed length.
:param size: string length, defaults to 1
:type size: int, optional
:param amount: amount of random strings to generate, defaults to 1
:type amount: int, optional
:yield: Yield composed random string if unique
:rtype: Generator[str, None, None]
"""
CHARS = list(ascii_uppercase + digits)
LIMIT = len(CHARS) ** size
count, check, string = 0, set(), ''
while LIMIT > count < amount:
string = ''.join(RND().choices(CHARS, k=size))
if string not in check:
check.add(string)
yield string
count += 1
for my_count, my_string in enumerate(string_generator(6, 20)):
print(my_count, my_string)
Output:
0 RS9N3P
1 S0GDGR
2 ZNBLFV
3 96FF97
4 38JJZ3
5 Q3214A
6 VLWNK1
7 QMT05E
8 X1ZFP0
9 MZF442
10 10L9AZ
11 GE8HIQ
12 S7PA43
13 MVLXO9
14 YX7Y0G
15 GIIKPF
16 3KCUQA
17 XHIXFV
18 BJQ5VG
19 HQF01Q
If your string always needs to contain letters and numbers, use this:
#!/usr/bin/env python
from typing import Generator
from random import SystemRandom as RND
from string import ascii_uppercase, digits
def string_generator(size: int = 2, amount: int = 1) -> Generator[str, None, None]:
"""
Return x random strings of a fixed length.
:param size: string length, defaults to 1
:type size: int, optional
:param amount: amount of random strings to generate, defaults to 1
:type amount: int, optional
:yield: Yield composed random string if unique
:rtype: Generator[str, None, None]
"""
if size < 2:
print(
'Since the string must contain letters and numbers,',
'its size must be at least two characters',
)
return
CHARS = list(ascii_uppercase + digits)
LIMIT = len(CHARS) ** size
count, check, string = 0, set(), ''
while LIMIT > count < amount:
while 1:
string = ''.join(RND().choices(CHARS, k=size))
if not (string.isalpha() or string.isnumeric()):
break
if string not in check:
check.add(string)
yield string
count += 1
for my_count, my_string in enumerate(string_generator(6, 20)):
print(my_count, my_string)
Output:
0 5JIITL
1 3W7AI1
2 8QMO10
3 ETHAI8
4 BLFPP9
5 50X2CC
6 1LI8WA
7 39CKET
8 R4IM0E
9 Q3KHGS
10 65CBIU
11 XTRHO4
12 N2XIGO
13 06VFCW
14 VE9MJ8
15 A9ADHK
16 Y5ROJ0
17 OH7EJF
18 TQ709S
19 P0DDNJ
Upvotes: -1
Reputation: 226524
Our recommendation for anything security related is to avoid "rolling you own" and to use the secrets module which is specifically vetted for security.
This is from the best practices section of the docs:
import string
import secrets
alphabet = string.ascii_letters + string.digits
password = ''.join(secrets.choice(alphabet) for i in range(8))
Since you specifically asked for uppercase letters, you can either substitute ascii_uppercase
for ascii_letters
, or just uppercase the password with:
password = password.upper()
The canonical approach to this problem (as specified) uses the choices() function in the random module:
>>> from random import choices
>>> from string import ascii_uppercase, digits
>>> population = ascii_uppercase + digits
>>> str.join('', choices(population, k=6))
'6JWF1H'
Upvotes: 12
Reputation: 855
I used this method to generate random string of length n from a -> z
import random
s = ''.join(random.choice([chr(i) for i in range(ord('a'),ord('z'))]) for _ in range(10))
Upvotes: 4
Reputation: 152735
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!
Upvotes: 27
Reputation: 799130
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 this post
''.join(random.SystemRandom().choice(string.ascii_uppercase + string.digits) for _ in range(N))
In details, with a clean function for further reuse:
>>> import string
>>> import random
>>> def id_generator(size=6, chars=string.ascii_uppercase + string.digits):
... return ''.join(random.choice(chars) for _ in range(size))
...
>>> id_generator()
'G5G74W'
>>> 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:
>>> string.ascii_uppercase
'ABCDEFGHIJKLMNOPQRSTUVWXYZ'
>>> string.digits
'0123456789'
>>> string.ascii_uppercase + string.digits
'ABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789'
Then we use a list comprehension to create a list of 'n' elements:
>>> range(4) # range create a list of 'n' numbers
[0, 1, 2, 3]
>>> ['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:
>>> random.choice("abcde")
'a'
>>> random.choice("abcde")
'd'
>>> 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
:
>>> [random.choice('abcde') for _ in range(3)]
['a', 'b', 'b']
>>> [random.choice('abcde') for _ in range(3)]
['e', 'b', 'e']
>>> [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:
>>> ''.join(['a', 'b', 'b'])
'abb'
>>> [random.choice('abcde') for _ in range(3)]
['d', 'c', 'b']
>>> ''.join(random.choice('abcde') for _ in range(3))
'dac'
Upvotes: 3280
Reputation: 29571
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)
Upvotes: 0
Reputation: 850
you can now use a new library (python >= 3.6) chancepy
here
from chancepy import Chance
random_string = Chance.string(length=10, pool="someLettersAndNumbers123")
Upvotes: -2
Reputation: 1715
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.
Upvotes: -1
Reputation: 11249
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.
Upvotes: 3
Reputation: 98991
import string, random
lower = string.ascii_lowercase
upper = string.ascii_uppercase
digits = string.digits
special = '!"£$%^&*.,@#/?'
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
Upvotes: 1
Reputation: 2000
Generate random 16-byte ID containig letters, digits, '_' and '-'
os.urandom(16).translate((f'{string.ascii_letters}{string.digits}-_'*4).encode('ascii'))
Upvotes: 2
Reputation: 6669
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.
Upvotes: 656
Reputation: 6787
Sometimes 0 (zero) & O (letter O) can be confusing. So I use
import uuid
uuid.uuid4().hex[:6].upper().replace('0','X').replace('O','Y')
Upvotes: 5
Reputation: 5190
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')
Upvotes: -1
Reputation: 636
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:
>>> from strgen import StringGenerator as SG
>>> SG("[\u\d]{6}").render()
u'YZI2CI'
Get a unique list:
>>> 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:
>>> SG("[\l\d]{10}&[\p]").render()
u'jaYI0bcPG*0'
A random HTML color:
>>> 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.
Upvotes: 21
Reputation: 31
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>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.
Upvotes: 2
Reputation: 26507
If UUIDs are okay for your purposes, use the built-in uuid package.
import uuid; uuid.uuid4().hex.upper()[0:6]
Example:
import uuid
uuid.uuid4() #uuid4 => 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
Upvotes: 280
Reputation: 894
Two methods :
import random, math
def randStr_1(chars:str, length:int) -> 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) -> 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) -> 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) -> 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.
Upvotes: 1
Reputation: 1654
import uuid
lowercase_str = uuid.uuid4().hex
lowercase_str
is a random value like 'cea8b32e00934aaea8c005a35d85a5c0'
uppercase_str = lowercase_str.upper()
uppercase_str
is 'CEA8B32E00934AAEA8C005A35D85A5C0'
Upvotes: 39
Reputation: 133
>>> import string
>>> import random
the following logic still generates 6 character random sample
>>> print ''.join(random.sample((string.ascii_uppercase+string.digits),6))
JT7K3Q
No need to multiply by 6
>>> print ''.join(random.sample((string.ascii_uppercase+string.digits)*6,6))
TK82HK
Upvotes: 4
Reputation: 2973
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]
Upvotes: 1
Reputation: 4213
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
Upvotes: 6
Reputation: 1290
I found this to be simpler and cleaner.
str_Key = ""
str_FullKey = ""
str_CharacterPool = "01234ABCDEFfghij~>()"
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.
Upvotes: -3
Reputation: 33
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 <= 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()
Upvotes: 3
Reputation: 525
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
Upvotes: 2
Reputation: 59
(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
Upvotes: 3
Reputation: 11130
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]
>>> from tools import irand_seqs
>>> strings = irand_seqs()
>>> a = next(strings)
>>> assert isinstance(a, (str, unicode))
>>> assert len(a) == 6
>>> 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:
>>> irand_tuples = irand_seqs(xrange(10), join=tuple)
>>> next(irand_tuples)
(0, 5, 5, 7, 2, 8)
>>> 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:
>>> irand_tuples = irand_seqs(xrange(10), join=tuple)
>>> make_rand_tuples = partial(next, irand_tuples)
>>> make_rand_tuples()
(1, 6, 2, 8, 1, 9)
if you want to generate the sequence on the fly simply set join to identity.
>>> irand_tuples = irand_seqs(xrange(10), join=identity)
>>> selections = next(irand_tuples)
>>> next(selections)
8
>>> list(selections)
[6, 3, 8, 2, 2]
As others have mentioned if you need more security then set the appropriate select function:
>>> from random import SystemRandom
>>> 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:
>>> from random import sample
>>> irand_samples = irand_seqs(xrange(10), length=1, join=next, select=lambda pool: sample(pool, 6))
>>> 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 ...
Upvotes: 3
Reputation: 19753
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
Upvotes: 1