Asked about Thinking in arrays
What does SettingWithCopyWarning mean?
An answer that works
You may be assigning to a copy rather than the original DataFrame, so the change silently does nothing. It usually follows a filter, and using .loc for conditional assignment avoids both the warning and the bug.
Reading an answer is not being able to give one. The section that teaches this is Thinking in arrays, 6 hours of NumPy & pandas.
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