How to assign the result of a for loop to a variable in Python

Question

My program generates a random string with a random amount of letters from 10 to 20.

def program():
    import random
    import sys
    x=['q','w','e','r']
    y=random.randint(10,20)
    for t in range (0,y):
       w=random.randint(0,3)
       e=x[w]
       sys.stdout.write(e)

The program will print a random string like 'wwwweewwqqrrrrwwqqeeqqww'. How would I store this string as a variable?

Instead of writing, store the result into a string or array. — user3483203, Apr 17 '18 at 20:40
As a side note: `e = random.choice(x)` is much more readable than `w = random.randint(0, 3); e = x[w]`. — abarnert, Apr 17 '18 at 20:43
In fact, you could replace this entire function with `return ''.join(random.choices('qwer', k=random.randint(10, 20)))` — abarnert, Apr 17 '18 at 20:44

Xantium · Accepted Answer · 2018-04-17T20:52:49.583

Store it in a variable instead of writing:

e=''

for t in range (0,y):
    w=random.randint(0,3)
    e += x[w]

e is an empty variable and each time you add the value x[w] to it.

I would also recommend using print() over sys.stdout.write(e) since you do not need additional imports -such as sys, print() is inbuilt.

In this case can I suggest the use of a tuple for x=['q','w','e','r'] since they are faster. So: x=('q','w','e','r'1)

but if you are going to need to modify this later then this is not an option available to you (since they are immutable).

user3483203 · Answer 2 · 2018-04-17T20:49:06.410

3

You could replace your loop with a list comprehension, and use join():

e = ''.join([random.choice(x) for _ in range(0, y)])

Output:

qwewwwereeeqeqww

edited Apr 17 '18 at 20:49

answered Apr 17 '18 at 20:43

user3483203

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I like this answer, but I feel like it would be hard to understand for someone who's new to python (like the OP seems to be). – Aaron N. Brock Apr 17 '18 at 20:47

score 2 · Answer 3 · answered Apr 17 '18 at 20:43

2

def program():
   import random
   x=['q','w','e','r']
   y=random.randint(10,20)
   mystr=''
   for t in range (0,y):
      w=random.randint(0,3)
      e=x[w]
      mystr=mystr+e

answered Apr 17 '18 at 20:43

Anonymous

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Could you provide an explanation with your code so that the OP and future visitors know what you have done. – Xantium Apr 17 '18 at 20:57

score 1 · Answer 4 · answered Apr 17 '18 at 20:46

If you'd like you can haveprogram() returns the output variable like so:

def program():
    import random
    import sys
    x=['q','w','e','r']
    y=random.randint(10,20)
    output = ''
    for t in range (0,y):
        w=random.randint(0,3)
        e=x[w]
        output+=e
    # The print is stored in 'output'

    # Return the output
    return output
result = program()

score 1 · Answer 5 · answered Apr 17 '18 at 20:49

An easy way to do this would be to create a new string variable and just use the += operator to concatenate each character onto a new string. Your code could be

 def program():
   import random
   import sys
   x=['q','w','e','r']
   y=random.randint(10,20)
   z = '';
   for t in range (0,y):
      w=random.randint(0,3)
      e=x[w]
      z += e;

This code just adds each character to a string variable z in your for loop, and that string value should be stored in z.

score 1 · Answer 6 · answered Apr 17 '18 at 20:54

something like (haven't tested the program, should work... famous last words).

# imports at start of file, not in def
import random
import sys

# I would never call a def 'program', kind of generic name, avoid
def my_program():  # camel case, PEP-8
    x=['q','w','e','r']
    z=''  # initialize result as an empty string
    for _ in range (0, random.randint(10,20)):
       z+=x[random.randint(0,3)]  # add a letter to string z
    return z

"_" is often used for a throw away variable, see What is the purpose of the single underscore "_" variable in Python? In this case the _ is used nowhere.

How to assign the result of a for loop to a variable in Python

6 Answers6