In [6]:
import random

fh = open(r'd:\temp\wordlist.txt')
text = fh.read()
idioms = text.split(' ') 
print(idioms)
fh.close()

for number in range(len(idioms)): 
    n = len(idioms[number]) 
    key =  random.randint(100000000,999999999)
    new_key = str(key) + str(key) 
    print(new_key)
    new_idioms = []
    for i in range(len(idioms[number])):
        word = ord((idioms[number])[i]) + ord(new_key[i])-48
        if 97 < word < 122:
            new_idioms.append(chr(word))
        elif word > 122:
            new_idioms.append(chr(word-26))
    idioms[number] = new_idioms
    
    if n < 10:
        for x in range(n,10):
            idioms[number]= idioms[number]+''.join(random.sample(string.ascii_letters,(10-len(words[i]))))
            idioms[numeber]=idioms[number].lower()
    
print(idioms)

fh = open(r'd:\temp\wordlist_new.txt', 'w')
fh.writelines(str(idioms))
fh.close()


['the', 'story', 'of', 'our', 'english', 'language', 'is', 'typically', 'one', 'of', 'massive', 'stealing', 'from', 'other', 'language', 'that', 'is', 'why', 'english', 'today', 'has\nan', 'estimated', 'vocabulary', 'of', 'over', 'one', 'million', 'words', 'while', 'other', 'major', 'laguages', 'have', 'far', 'fewer']
264716740264716740
---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)
<ipython-input-6-0df63aa43496> in <module>()
     23     if n < 10:
     24         for x in range(n,10):
---> 25             idioms[number]= idioms[number]+''.join(random.sample(string.ascii_letters,(10-len(words[i]))))
     26             idioms[numeber]=idioms[number].lower()
     27 

TypeError: can only concatenate list (not "str") to list