Create python string from object values

Question

I don't know the best way to describe what I am really looking for probably this example is the best for explaining my problem:

I have the following list of strings (my object names):

mynames = ["A","B","C"]

my objects itself are defined as:

A = "Hello"
B = 12
C = "This is C"

Now I'd like to create a comma-separated string with all values of the objects mentioned in "mynames" like:

myresult = "Hallo,12,This is C"

of course I could do it manually like:

",".join([A,str(B),C])

but is there a way to create the result based on the list "mynames", something like ",".join(mynames)??

thanks,

/j

How about mynames list storing the objects instead of strings?, is there any reason for it? — Netwave
– Netwave, Commented Oct 11, 2012 at 8:41

georg · Accepted Answer · 2012-10-11 08:43:49Z

4

The obvious answer is to use globals() or locals() as in

lst = [globals()[x] for x in 'A', 'B', 'C']

and the correct one is

 don't do that

Every time you attempt to manipulate variable names in python you're doing a wrong thing. Use an appropriate data structure, like dict.

answered Oct 11, 2012 at 8:43

georg

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3 Comments

eumiro Over a year ago

SO should change the syntax highlighting for some important messages, such as don't do that

Katriel Over a year ago

I believe there is a way to indicate the language for syntax highlighting -- some sort of funky comment -- but I can't remember it.

unutbu Over a year ago

@katrielalex:

Inbar Rose · Accepted Answer · 2012-10-11 09:03:33Z

2

as mentioned in other answers, you can use eval, literal-eval, globals, locals, or other such nonsense to complete your task - but your approach is wrong.

as i think is mentioned in other answers, you are better off using a different data structure, a dictionary perhaps. for instance, in your example:

A = "Hello"
B = 12
C = "This is C"

can be done with:

my_dict = {}
my_dict["A"] = "Hello"
my_dict["B"] = 12
my_dict["C"] = "This is C"

and then you can simply do this:

mynames = ["A","B","C"]
print [my_dict[key] for key in mynames]

on the console, this is the result:

>>> my_dict = {}
>>> my_dict["A"] = "Hello"
>>> my_dict["B"] = 12
>>> my_dict["C"] = "This is C"
>>> mynames = ["A","B","C"]
>>> print [my_dict[key] for key in mynames]
['Hello', 12, 'This is C']

making them into one string is simple now, and im sure you can take it from here.

answered Oct 11, 2012 at 9:03

Inbar Rose

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2 Comments

Johannes Over a year ago

Thanks, works perfectly of course. I have to focus more on the usage of dictionaries... :)

Inbar Rose Over a year ago

dictionaries are great. and there are many more types of data structures, each with their own ideal uses. dicts however, are a great backbone. when dealing with many different variables that are all related - a dict is almost a must. and since python doesnt care much for types, your dictionary can of course, contain anything, even more dictionaries.

michel-lind · Accepted Answer · 2012-10-11 08:44:38Z

0

eval is your friend here:

",".join([ str(eval(e)) for e in mynames ])

answered Oct 11, 2012 at 8:44

michel-lind

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