Here are a few title options that fit the question-and-answer format, are in English, and accurately reflect the article\'s content: * **DataFrame Construction with Scalars: Why \"ValueError\&qu

Constructing DataFrame from Scalars: Resolving "ValueError" Exception

Problem:

When attempting to construct a DataFrame using scalar values in variables, the following error is encountered:

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

This occurs when the DataFrame is initialized using a dictionary where all values are scalars, as in the following example:

<code class="python">a = 2
b = 3
df2 = pd.DataFrame({'A': a, 'B': b})</code>

Solution:

To resolve this issue, there are two options:

1. Use Non-Scalar Values for Columns:

Instead of using scalar values for columns, use lists:

<code class="python">df = pd.DataFrame({'A': [a], 'B': [b]})</code>

2. Pass an Index with Scalar Values:

If scalar values must be used, pass an index along with the dictionary:

<code class="python">df = pd.DataFrame({'A': a, 'B': b}, index=[0])</code>

This provides the necessary context for the DataFrame to understand the structure of the data.

Example:

The following code demonstrates the correct method for constructing a DataFrame using scalar values:

<code class="python">a = 2
b = 3
df = pd.DataFrame({'A': [a], 'B': [b]}, index=[0])
print(df)</code>

Output:

   A  B
0  2  3

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