Question

我有一个sqlite3数据库列表，希望能够通过循环将每个数据库读取到单独的Pandas Dataframe中，但到目前为止，我的方法尚未填充该数据帧。我想这与处理副本而不是参考有关，但是找不到一种可行的方法。

import sqlite3
import pandas as pd

db_1 = 'db1.db'
db_2 = 'db2.db'

df_1 = pd.DataFrame()
df_2 = pd.DataFrame()

db_df_name = [(db_1, df_1, 'df_raw'), (db_2, df_2, 'df_processed')]

for (db, df, name) in db_df_name:
with sqlite3.connect(db, detect_types=sqlite3.PARSE_DECLTYPES) as connection:
    df = pd.read_sql_query("select * from messages;", connection)
    print(f'Database {name} processed')

Answer 1

如果您可以更好地解释您想做什么，我可以提供更多帮助。

尝试一下，如果不起作用请纠正我：

import sqlite3
import pandas as pd

# Assuming that you have two databases... 
# which i don't understand cause you use the 
# same query below with the same table.
dbs = ['db1.db','db2.db']

db_df_name = [(dbs[0], 'df_raw'), (dbs[1],'df_processed')]

df_1 = pd.DataFrame()
df_2 = pd.DataFrame()

df_list = []
for db, name in db_df_name:
    with sqlite3.connect(db, detect_types=sqlite3.PARSE_DECLTYPES) as connection:
        df = pd.read_sql_query("select * from messages;", connection)
        print(f'Database {name} processed')
        df_list = df_list.append(df.copy())

df_1, df_2 = df_list
print(df_1)
print(df_2)

使用此命令时：for db, name in db_df_name， db 是作用域变量，它本身不是 df_1 ，假设您正在传递此结构（这就是我删除）：

db_df_name = [(db_1, df_1, 'df_raw'), (db_2, df_2, 'df_processed')]

因此，当您分配df = ...时， df_1 将为空。

分配pd.read_sql_query的结果Dataframes列表

1 个答案: