Constructing DataFrame from values in variables yields "ValueErr

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

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. How do I do what I want?

Answers

When constructing a pandas DataFrame from scalar values, pandas requires an index because it interprets scalar values as needing to be broadcasted across rows. To solve this issue, you can either:

1. Wrap the scalar values in a list (which pandas will interpret as single-row data).
2. Pass the index explicitly.

Here are two ways you can do this:

1. Wrapping the scalars in a list:

This is the simplest way to convert scalar values into a DataFrame:

import pandas as pd

a = 2
b = 3

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

Output:

   A  B
0  2  3

2. Explicitly passing an index:

Alternatively, you can pass an index if you want more control over the DataFrame structure:

df2 = pd.DataFrame({'A': a, 'B': b}, index=[0])
print(df2)

Output:

   A  B
0  2  3

Both methods will give you a single-row DataFrame where a and b are values in columns A and B, respectively.