在 pandas 中读取镶木地板文件（read_parquet()）时如何保留 dtypes？

Question

Code:

In [31]: df = pd.DataFrame({"a": [[{"b": 1}], [{"b": np.nan}]]})

In [32]: df
Out[32]:
              a
0    [{'b': 1}]
1  [{'b': nan}]

In [33]: df.dtypes
Out[33]:
a    object
dtype: object

In [34]: df.to_parquet("a.parquet")

In [35]: pd.read_parquet("a.parquet")
Out[35]:
               a
0   [{'b': 1.0}]
1  [{'b': None}]

As you can see here, [{'b': 1}] becomes [{'b': 1.0}] .

How can I keep dtypes even in reading the parquet file?

Answer 1

Try to turn on use_nullable_dtypes

df = pd.DataFrame({"a": [[{"b": 1}], [{"b": None}]]})
df.dtypes

df.to_parquet("a.parquet")
pd.read_parquet("a.parquet", use_nullable_dtypes=True)

	a
0	[{'b': 1.0}]
1	[{'b': None}]

See the pandas doc for more explaination