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How do you create different variable names while in a loop?


Question

For example purposes...

for x in range(0,9):
    string'x' = "Hello"

So I end up with string1, string2, string3... all equaling "Hello"

2017/12/22
1
126
12/22/2017 6:32:54 AM

Accepted Answer

Sure you can; it's called a dictionary:

d = {}
for x in range(1, 10):
    d["string{0}".format(x)] = "Hello"
>>> d["string5"]
'Hello'
>>> d
{'string1': 'Hello',
 'string2': 'Hello',
 'string3': 'Hello',
 'string4': 'Hello',
 'string5': 'Hello',
 'string6': 'Hello',
 'string7': 'Hello',
 'string8': 'Hello',
 'string9': 'Hello'}

I said this somewhat tongue in check, but really the best way to associate one value with another value is a dictionary. That is what it was designed for!

2020/06/13
167
6/13/2020 10:33:14 PM


One way you can do this is with exec(). For example:

for k in range(5):
    exec(f'cat_{k} = k*2')
>>> print(cat_0)
0
>>> print(cat_1)
2
>>> print(cat_2)
4
>>> print(cat_3)
6
>>> print(cat_4)
8

Here I am taking advantage of the handy f string formatting in Python 3.6+

2020/06/13

It's simply pointless to create variable variable names. Why?

  • They are unnecessary: You can store everything in lists, dictionarys and so on
  • They are hard to create: You have to use exec or globals()
  • You can't use them: How do you write code that uses these variables? You have to use exec/globals() again

Using a list is much easier:

# 8 strings: `Hello String 0, .. ,Hello String 8`
strings = ["Hello String %d" % x for x in range(9)]
for string in strings: # you can loop over them
    print string
print string[6] # or pick any of them
2011/05/31

Don't do this use a dictionary

import sys
this = sys.modules[__name__] # this is now your current namespace
for x in range(0,9):
    setattr(this, 'string%s' % x, 'Hello')

print string0
print string1
print string2
print string3
print string4
print string5
print string6
print string7
print string8

don't do this use a dict

globals() has risk as it gives you what the namespace is currently pointing to but this can change and so modifying the return from globals() is not a good idea

2017/04/12

for x in range(9):
    exec("string" + str(x) + " = 'hello'")

This should work.

2020/06/13

I would use a list:

string = []
for i in range(0, 9):
  string.append("Hello")

This way, you would have 9 "Hello" and you could get them individually like this:

string[x]

Where x would identify which "Hello" you want.

So, print(string[1]) would print Hello.

2011/05/31

Source: https://stackoverflow.com/questions/6181935
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