pandas 中 GroupBy 对象的属性

Question

I believe this piece of code could access name and group attributes using iterator, however, what other attributes of GroupBy objects could I access, and where could I find attributes of GroupBy objects except these two, as I haven't found them on pandas documents.

for name, group in GroupBy:

Answer 1

GroupBy returns an GroupBy object , which not only is an iterable containing key/group tuples, but being an object, you can access its parameters as attributes.

Let's take the following dataframe as an example:

df = pd.DataFrame({'a':[1,2,3,2,2,3], 'b':[1,2,3,3,2,1]})

As mentioned, by iterating over the returned object, we get the key/group tuples that group the dataframe according to the key :

g = df.groupby('a')
key, group = next(iter(g))

print(key)
# 1

print(group)
   a  b
0  1  1

This is the what is returned by its __iter__ dunder, next(g.__iter__()) , which calls get_iterator :

def get_iterator(self, data: FrameOrSeries, axis: int = 0):
    """
    Groupby iterator
    Returns
    -------
    Generator yielding sequence of (name, subsetted object)
    for each group
    """
    splitter = self._get_splitter(data, axis=axis)
    keys = self._get_group_keys()
    for key, (i, group) in zip(keys, splitter):
        yield key, group

Its attributes can be accessed just as you would with any other object:

g.__dict__
{'_selection': None,
 'level': None,
 'as_index': True,
 'keys': 'a',
 'sort': True,
 'group_keys': True,
 'squeeze': False,
 'observed': False,
 'mutated': False,
 'obj':    a  b
 0  1  1
 1  2  2
 2  3  3
 3  2  3
 4  2  2
 5  3  1,
 'axis': 0,
 'grouper': <pandas.core.groupby.ops.BaseGrouper at 0x17399312eb0>,
 'exclusions': {'a'}}

g.sort
# True