Pseudo-random number generators work by performing some operation on a value. Generally this value is the previous number generated by the generator. However, the first time you use the generator, there is no previous value.

Seeding a pseudo-random number generator gives it its first "previous" value. Each seed value will correspond to a sequence of generated values for a given random number generator. That is, if you provide the same seed twice, you get the same sequence of numbers twice.

Generally, you want to seed your random number generator with some value that will change each execution of the program. For instance, the current time is a frequently-used seed. The reason why this doesn't happen automatically is so that if you want, you can provide a specific seed to get a known sequence of numbers.

For the integers:

import random 

def random_seed(length):
    random.seed()
    min = 10**(length-1)
    max = 9*min + (min-1)
    return random.randint(min, max)

For the strings, a naive approach may be:

import random

choices = '0123456789abcdefghijklmnopqrstuvwxyz'

def random_char(pos):
   return random.choice(choices)

def random_seed(length):
  l = [None]*length
  random.seed()
  return "".join(list(map(random_char, l)))

Beware, this shouldn't be used for security purpose you must rely on os.urandom instead.