Instruction: Provide a detailed comparison between the 'merge' and 'join' methods, including their default behaviors.
Context: Candidates should demonstrate their understanding of the nuances between merging and joining DataFrames, including how indexes play a role in each method.
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The 'merge' function in Pandas is fundamentally used for combining two DataFrames based on one or more keys. This is somewhat akin to SQL JOIN operations. By default, 'merge' performs an inner join, meaning it returns only those rows that have common characteristics in both DataFrames. The key columns on which the merge is performed can be specified using the 'on' parameter, and if not specified, Pandas will use columns with the same names in both DataFrames. It's also versatile, allowing for left, right, and outer joins through the 'how' parameter.
On the other hand, the 'join' method is more index-focused. While 'merge' can be used with both...