What's the best way to generate random strings of a specific length in Python?
CODE:
from random import choice
from string import ascii_uppercase
print(''.join(choice(ascii_uppercase) for i in range(12)))
OUTPUT:
5 examples:
QPUPZVVHUNSN
EFJACZEBYQEB
QBQJJEEOYTZY
EOJUSUEAJEEK
QWRWLIWDTDBD
EDIT:
If you need only digits, use the digits
constant instead of the ascii_uppercase
one from the string
module.
3 examples:
229945986931
867348810313
618228923380
By Django
, you can use get_random_string
function in django.utils.crypto
module.
get_random_string(length=12,
allowed_chars=u'abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789')
Returns a securely generated random string.
The default length of 12 with the a-z, A-Z, 0-9 character set returns
a 71-bit value. log_2((26+26+10)^12) =~ 71 bits
Example:
get_random_string()
u'ngccjtxvvmr9'
get_random_string(4, allowed_chars='bqDE56')
u'DDD6'
But if you don't want to have Django
, here is independent code of it:
Code:
import random
import hashlib
import time
SECRET_KEY = 'PUT A RANDOM KEY WITH 50 CHARACTERS LENGTH HERE !!'
try:
random = random.SystemRandom()
using_sysrandom = True
except NotImplementedError:
import warnings
warnings.warn('A secure pseudo-random number generator is not available '
'on your system. Falling back to Mersenne Twister.')
using_sysrandom = False
def get_random_string(length=12,
allowed_chars='abcdefghijklmnopqrstuvwxyz'
'ABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789'):
"""
Returns a securely generated random string.
The default length of 12 with the a-z, A-Z, 0-9 character set returns
a 71-bit value. log_2((26+26+10)^12) =~ 71 bits
"""
if not using_sysrandom:
# This is ugly, and a hack, but it makes things better than
# the alternative of predictability. This re-seeds the PRNG
# using a value that is hard for an attacker to predict, every
# time a random string is required. This may change the
# properties of the chosen random sequence slightly, but this
# is better than absolute predictability.
random.seed(
hashlib.sha256(
("%s%s%s" % (
random.getstate(),
time.time(),
SECRET_KEY)).encode('utf-8')
).digest())
return ''.join(random.choice(allowed_chars) for i in range(length))
Could make a generator:
from string import ascii_uppercase
import random
from itertools import islice
def random_chars(size, chars=ascii_uppercase):
selection = iter(lambda: random.choice(chars), object())
while True:
yield ''.join(islice(selection, size))
random_gen = random_chars(12)
print next(random_gen)
# LEQIITOSJZOQ
print next(random_gen)
# PXUYJTOTHWPJ
Then just pull from the generator when they're needed... Either using next(random_gen)
when you need them, or use random_200 = list(islice(random_gen, 200))
for instance...