The API of methods taking udf follow certain patterns that make them consistent and easier to learn and use. There are some small differences, which have been listed in #40112 and #61128.

This issue is to rename the arg parameter of Series.map to func, which is the name consistently used in almost all methods. In the case of Series.map, the argument is slightly different than others, given that arg or func can also be a dict or a Series, which will make map replace values from these mappings, instead of executing an elementwise udf.

This issue is for the renaming of the parameter, making the parameter consistent with other methods such as DataFrame.apply can be considered in another issue. But there are some cases to consider, given that the behavior of map is slightly different when providing a mapping, than when providing a function that maps. In particular, map will use NaN when the mapping returns None, but it will use None when the function returns None. Also, if we stop supporting dictionaries, users in general should just replace their code from Series.map(my_dict) to Series.map(my_dict.get). But there are some special cases, for example when the dictionary is a defaultdict, .get will return None, while the current map implementation with a defaultdict will consider the default value.