Pandas 元数据属性未传递给 Groupby 的组 Object

Question

Suppose I have

df = pd.DataFrame({'A': [1,2,3], 'B': [1,2,1]})
df._metadata += "name"
df.name = "The Name"

groups = df.groupby(by="B")
for id, group in groups:
    print(group.name)

The print function will throw an AttributeError .

Now, I would need to somehow pass the metadata to each individual group. How can this be done?

Answer 1

You should use this notation ( df['COLNAME'] = 'VALUE' ) to add new columns:

df = pd.DataFrame({'A': [1,2,3], 'B': [1,2,1]})
df['_metadata'] = "name"
df['name'] = "The Name"

groups = df.groupby(by="B")
for id, group in groups:
    print(group.name)

Output:

0    The Name
2    The Name
Name: name, dtype: object
1    The Name
Name: name, dtype: object

Answer 2

You could still access it from df , no?

# ...
for id, group in groups:
    print(df.name)

You could also then assign to each group if you need to do that for whatever reason:

# ...
for id, group in groups:
    group.name = df.name