Need to check all my variables for an ampersand, I put variables in a list and check using a for loop, but Python only changes value inside list

I’ve got the following code, but unfortunately it only changes the value inside the list. Is there any way I can change the value outside the list, so it can be used later in the script?

street_number = "100 & 102"
street_name = "Fake Street"
suburb = "Faketown"

allvariables = [street_number, street_name, suburb]

ampersand = "&"
ampersand_escape = "&"

for i, item in enumerate(allvariables):
    if isinstance(item, str):
        if ampersand in item:
            allvariables[i] = item.replace(ampersand,ampersand_escape)

print(allvariables) # -> ['100 & 102', 'Fake Street', 'Faketown']
print(street_number) # -> 100 & 102

The only alternative I can imagine is checking each variable individually, but I’ve got a LOT of variables that need to be checked so it would take forever:

if ampersand in street_number:

if ampersand in street_name:

if ampersand in suburb:

But that seems extremely time consuming. Thank you in advance for your help!

P.S. just in case – I need to do a few more checks besides the ampersands

>Solution :

Each variable in python (for instance, street_number) is just a reference to something. In this case, street_number is a reference to a string, namely "100 & 102".

When you write allvariables = [street_number, street_name, suburb], you are simply creating a list with elements that have been initialized by the variables. So in your list, position 0 contains a string which was copied from street_number and has the same value "100 & 102", but there is no ongoing linkage to the variable street_number.

So if you update allvariables[0] to be ‘100 & 102’, this will have no effect on the value referenced by the variable street_number.

One way to get the result I think you want would be this:

street_number = "100 & 102"
street_name = "Fake Street"
suburb = "Faketown"

allvariableNames = ['street_number', 'street_name', 'suburb']

ampersand = "&"
ampersand_escape = "&"

ampIndices = [i for i, item in enumerate(allvariableNames) if isinstance(eval(item), str) and ampersand in eval(item)]
for i in ampIndices:
    exec(f'{allvariableNames[i]} = {allvariableNames[i]}.replace(ampersand, ampersand_escape)')
print(', '.join(f"'{eval(item)}'" for item in allvariableNames)) # -> ['100 & 102', 'Fake Street', 'Faketown']


'100 & 102', 'Fake Street', 'Faketown'
100 & 102


  • instead of initializing a list using the variables you have in mind, initialize a list with the names of these variables as strings
  • build a list of the indices into the variable name list for the value of the variable (obtained using the eval() function) contains the search pattern
  • use exec() to execute a python statement that uses the string name of the variable to update the variable’s value by replacing the search pattern with the new string &amp

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