How to get value of variable entered from user input?

Question

I am trying to create a basic menu that checks to see if the variable entered matches a defined variable. If the variable is defined get the data of the defined variable.

Example.

Item1 = "bill"
Item2 = "cows"
item3 = "abcdef"
Choose_Item = input("Select your item: ")

I type in Item1
Choose_Item should equal "bill"

And what have you tried? This seems more like a code request than a question. — Hubro, Mar 01 '13 at 23:47

score 23 · Accepted Answer · answered Mar 01 '13 at 23:47

23

This seems like what you're looking for:

Choose_Item = eval(input("Select your item:  "))

This probably isn't the best strategy, though, because a typo or a malicious user can easily crash your code, overload your system, or do any other kind of nasty stuff they like. For this particular case, a better approach might be

items = {'item1': 'bill', 'item2': 'cows', 'item3': 'abcdef'}
choice = input("Select your item: ")
if choice in items:
    the_choice = items[choice]
else:
    print("Uh oh, I don't know about that item")

answered Mar 01 '13 at 23:47

Danica

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Bah you beat me to the punch with literally the same advice. +1 for the faster typer ;) – Dave Lasley Mar 01 '13 at 23:48
1

I was just typing a similar comment on your answer, so you won that race at least. :) – Danica Mar 01 '13 at 23:48
[Oof, I see `eval` on user input...](https://stackoverflow.com/questions/1832940/why-is-using-eval-a-bad-practice) – TrebledJ Jul 05 '19 at 11:06

score 4 · Answer 2 · edited Jul 05 '19 at 11:05

4

Two ways you could go about this. The bad way:

print(eval(Choose_Item))

The better way would be to use a dictionary

items = {'1':'bill','2':'cows'}
Choose_Item = input("Select your Item: ")
try:
    print(items[Choose_Item])
except KeyError:
    print('Item %s not found' % Choose_Item)

edited Jul 05 '19 at 11:05

TrebledJ

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answered Mar 01 '13 at 23:47

Dave Lasley

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FWIW: question is tagged python-3, so you'd want parens in that print statement, and you probably also want to print something in the exception case rather than just building a string and not doing anything with it. :) – Danica Mar 01 '13 at 23:50
But aren't random strings good programming etiquette? Good catch sir, another reason why you deserve this answer – Dave Lasley Mar 01 '13 at 23:52

score 4 · Answer 3 · answered Mar 01 '13 at 23:48

4

You'll need to use locals()[Choose_Item] if you want to choose a variable whose name is what the user produced.

A more conventional way to do this, though, is to use a dictionary:

items = {
    'Item1': 'bill',
    'Item2': 'cows',
    'Item3': 'abcdef',
}

... and then the value you want is items[Choose_Item].

answered Mar 01 '13 at 23:48

Borealid

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+1 - the locals approach is better than eval, in that it at least doesn't let a malicious user go and, well, evaluate code. :) Of course the dictionary approach is preferable. – Danica Mar 01 '13 at 23:55

How to get value of variable entered from user input?

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