Constructing pandas DataFrame from values in variables gives "ValueError: If using all scalar values, you must pass an index"

Question

This may be a simple question, but I can not figure out how to do this. Lets say that I have two variables as follows.

a = 2 b = 3 

I want to construct a DataFrame from this:

df2 = pd.DataFrame({'A':a,'B':b}) 

This generates an error:

ValueError: If using all scalar values, you must pass an index

I tried this also:

df2 = (pd.DataFrame({'a':a,'b':b})).reset_index() 

This gives the same error message.

Answer 1

The error message says that if you're passing scalar values, you have to pass an index. So you can either not use scalar values for the columns -- e.g. use a list:

>>> df = pd.DataFrame({'A': [a], 'B': [b]}) >>> df    A  B 0  2  3 

or use scalar values and pass an index:

>>> df = pd.DataFrame({'A': a, 'B': b}, index=[0]) >>> df    A  B 0  2  3 

Answer 2

You can also use pd.DataFrame.from_records which is more convenient when you already have the dictionary in hand:

df = pd.DataFrame.from_records([{ 'A':a,'B':b }]) 

You can also set index, if you want, by:

df = pd.DataFrame.from_records([{ 'A':a,'B':b }], index='A')