物件建立

Created: November-22, 2018
In [188]: s = pd.Series(["a","b","c","a","c"], dtype="category")

In [189]: s
Out[189]: 
0    a
1    b
2    c
3    a
4    c
dtype: category
Categories (3, object): [a, b, c]

In [190]: df = pd.DataFrame({"A":["a","b","c","a", "c"]})

In [191]: df["B"] = df["A"].astype('category')

In [192]: df["C"] = pd.Categorical(df["A"])

In [193]: df
Out[193]: 
   A  B  C
0  a  a  a
1  b  b  b
2  c  c  c
3  a  a  a
4  c  c  c

In [194]: df.dtypes
Out[194]: 
A      object
B    category
C    category
dtype: object