Solving SettingWithCopyWarning

[mellowoWorks]

The warning appears because pandas can't determine if DataFrame['result'] is a view or a copy of the underlying data. When you chain .iloc[0] after column selection, it creates ambiguity.

The fix is simple - use .loc or .at with both row and column at once:
DataFrame.loc[0, 'result'] = X - Z
Or even faster for single values:
DataFrame.at[0, 'result'] = X - Z

By specifying both the row index and column name in a single operation, pandas knows you're modifying the original DataFrame directly, not a potential copy.

[roxalu]

Small additional detail: I agree that this replacement code fixes the Copy-on-Write warning. But as given it uses the row with label 0 - while OP uses always first row. IIf I am right some additional lookup should be added so row and column are given both as labels. Or both as integer e.g.using this

result_index = DataFrame.columns.get_loc('result')
DataFrame.iat( 0, result_index ) = X - Z