python - Converting generator from read_sql in pandas to dataframe has failed

Question

I want to read data from my oracle, I use the pandas's read_sql and set the parameter chunksize=20000,

from sqlalchemy import create_engine
import pandas as pd
engine = create_engine("my oracle")
df = pd.read_sql("select clause",engine,chunksize=20000)

It returns a iterator, and I want to convert this generator to a dataframe usingdf = pd.DataFrame(df), but it's wrong, How can the iterator be converted to a dataframe?

标签： pythonpandas

Answer 1

这个迭代器可以连接起来，然后它返回一个数据框：

df = pd.concat(df)

您可以查看pandas.concat文件。

如果不能concat直接使用，请尝试以下方法：

gens = pd.read_sql("select clause",engine,chunksize=20000)
dflist = []
for gen in gens:
    dflist.append(gen)
df = pd.concat(dflist)