read_sql usage in functions

Question

I am trying to use Pandas' read_sql() (from sqlalchemy) inside a function, but it keeps returning string instead of a DataFrame.

Why is this happening and how it can be fixed?

When I do something like this:

table_name = pd.io.sql.read_sql(table_name, con=engine)

Everything works perfectly. But when I put the same in a function like this one:

def sql_reading(table_name, comment):
     table_name = pd.io.sql.read_sql(table_name, con=engine)
     print('\x1b[1;31m'+comment  +'\x1b[0m')
     table_name.info()
     return table_name

It returns with info about the DataFrame, but does not allow to me to use the result as a DataFrame:

sql_reading(some_table_from_a_query, "Some comment")

Prints some_table_from_a_query.info(), everything is fine.

But when I try to print out its head or tail, or use describe() literally in the next step, it returns with an error:

some_table_from_a_query.info()

AttributeError: 'str' object has no attribute 'info'

UPD: Return table_name didn't make any difference.

Would appreciate an explanation on why it happens and how to fix it.

You don't return anything from your function

IoaTzimas
– IoaTzimas

2021-06-24 14:02:49 +00:00
Commented Jun 24, 2021 at 14:02 — IoaTzimas
– IoaTzimas, Commented Jun 24, 2021 at 14:02
Try return table_name at the end of your function.

Gord Thompson
– Gord Thompson

2021-06-24 14:37:41 +00:00
Commented Jun 24, 2021 at 14:37 — Gord Thompson
– Gord Thompson, Commented Jun 24, 2021 at 14:37
@GordThompson Unfortunately, didn't work.

Ilya Dachkovsky
– Ilya Dachkovsky

2021-06-25 15:17:15 +00:00
Commented Jun 25, 2021 at 15:17 — Ilya Dachkovsky
– Ilya Dachkovsky, Commented Jun 25, 2021 at 15:17

Hammurabi · Accepted Answer · 2021-06-28 05:12:43Z

1

You are confusing the string 'table_name' with the actual dataframe, which you have also called 'table_name'. That's why you get the error that string (table_name) has no attribute 'info'. Try using different variable names for the table versus the dataframe, such as:

def sql_reading(table_name, comment):
     df_table_name = pd.io.sql.read_sql(table_name, con=engine)
     print('\x1b[1;31m'+comment  +'\x1b[0m')
     df_table_name.info()
     return df_table_name

answered Jun 28, 2021 at 5:12

Hammurabi

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