Create variable from string in python

Question

I have read a lot of posts about this subject but I haven't found an answer to my problem.

Wants to write a function that allows you to create DF with different names and columns.

So I try this:

def createDT(name,c1,c2,c3):
    name = pd.DataFrame(columns = [c1,c2,c3])
    print(type(name))
    return name
createDT(DT,"col1","col2","col3")

and I receive:

NameError: name 'DT' is not defined

when I change the "name" variable to String I receives the message:

<class 'pandas.core.frame.DataFrame'>
and the table below

Which confirms the creation of DF, but if I want to call the DT variable I get a

NameError: name 'DT' is not defined

I know I can do it this way

DT2 = createDT(DT,"col1","col2","col3")

But then I have to name the variables again and I would like to avoid that and I want it to be written as a function. Any ideas on how to solve it?

U13-Forward · Accepted Answer · 2019-07-25 04:21:47Z

4

It's not that easy unfortunately:

def createDT(name,c1,c2,c3):
    globals()[name] = pd.DataFrame(columns = [c1,c2,c3])
    print(type(globals()[name]))
    return globals()[name]
createDT("DT","col1","col2","col3")

But a preferred and efficient solution would be:

def createDT(name,c1,c2,c3):
    return pd.DataFrame(columns = [c1,c2,c3])
createDT("col1","col2","col3")

edited Jul 25, 2019 at 4:21

answered Jul 24, 2019 at 10:07

U13-Forward

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4 Comments

Kepasere Over a year ago

Thank you so much. Could you also describe to me what was the problem and whether writing things this way is good programming practice?

U13-Forward Over a year ago

@Kepasere Because when you do name = ... it assigns a variable called name, not DT, also may you accept it as well?

juanpa.arrivillaga Over a year ago

@Kepasere this is absolutely not a good practice, and it is considered an antipattern

U13-Forward Over a year ago

@juanpa.arrivillaga Added a better one

julka · Accepted Answer · 2019-07-25 04:15:18Z

1

Wouldn't simple

def createDT(c1,c2,c3):
    temp = pd.DataFrame(columns = [c1,c2,c3])
    print(type(temp))
    return temp

DT = createDT("col1","col2","col3")

work?

In Python you (almost always) don't use function parameters as return value. And you don't need to worry about copying since in Python everything is (kind of like) pointers.

answered Jul 25, 2019 at 4:15

julka

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