将表从数据库导出到 mdf 文件

问题描述

我是python初学者。我有包含 5 个表的数据库，我使用 python 使用 asammdf 将所有这些表导出到 mdf 文件。

path_data = os.path.join('..\\Data','db_2021-05-06_11-49-42_day.db')
con = sqlite3.connect(path_data)
cursor = con.cursor()
cursor.execute('SELECT name FROM sqlite_master WHERE type="table";')
tables = cursor.fetchall()
print(tables)

sigs = []
for equipment in tables:
    df = pd.read_sql_query('select * from' + equipment,con)
    df_small = df[0:1000]
    df_time = (df_small['ts']-df_small.iloc[0]['ts'])
    df_time_int = df_time.astype('int64')
    for signal in df_small.columns.to_list():
        test_signal = Signal(samples=df_small[signal],timestamps=df_time,name=signal,unit='A')
        sigs.append(test_signal)
mdf.append(sigs)
mdf.save('test_complete.mf4',overwrite=True)

我发现这个错误：

TypeError                                 Traceback (most recent call last)
c:\Users\Muhammad Lazaroni\SW_Workspace\MeasurementMerger\Scripts\merger.py in 
      37 # table_list= list[tables]
      38 for equipment in tables:
----> 39     df = pd.read_sql_query('select * from' + equipment,con)
      40     df_small = df[0:1000]
      41     df_time = (df_small['ts']-df_small.iloc[0]['ts'])

TypeError: can only concatenate str (not "tuple") to str

解决方法

短语“can only concatenate str (not "tuple") to str”的意思是“试图连接 str 和 non-str (tuple)”。 因此，我们需要匹配我们尝试组合的任一类型。

df = pd.read_sql_query('select * from' + str(equipment),con)

df = pd.read_sql_query('select * from' + equipment,str(con))

尝试其中任何一个。