ENH: Clearer error messaging when pd.DataFrame.to_sql() receives an empty string for name param

[tmccall8829]

Feature Type

• Adding new functionality to pandas

• Changing existing functionality in pandas

• Removing existing functionality in pandas

Problem Description

We use the .to_sql() method quite often in our data pipelines. As a part of our testing framework, we pass an empty string to the name param in pd.DataFrame.to_sql(), like so:

# set up connection obj, create dataframe, etc.
...
df.to_sql(name="", con=sql_conn)
...

This returns an error, which is what you'd expect, but the error is remarkably massive and unclear:

Traceback (most recent call last):
  File "<stdin>", line 3, in <module>
  File "/Users/tom/opt/anaconda3/envs/hc/lib/python3.10/site-packages/pandas/core/generic.py", line 2986, in to_sql
    return sql.to_sql(
  File "/Users/tom/opt/anaconda3/envs/hc/lib/python3.10/site-packages/pandas/io/sql.py", line 696, in to_sql
    return pandas_sql.to_sql(
  File "/Users/tom/opt/anaconda3/envs/hc/lib/python3.10/site-packages/pandas/io/sql.py", line 1729, in to_sql
    table = self.prep_table(
  File "/Users/tom/opt/anaconda3/envs/hc/lib/python3.10/site-packages/pandas/io/sql.py", line 1632, in prep_table
    table.create()
  File "/Users/tom/opt/anaconda3/envs/hc/lib/python3.10/site-packages/pandas/io/sql.py", line 839, in create
    self._execute_create()
  File "/Users/tom/opt/anaconda3/envs/hc/lib/python3.10/site-packages/pandas/io/sql.py", line 825, in _execute_create
    self.table.create(bind=self.pd_sql.connectable)
  File "/Users/tom/opt/anaconda3/envs/hc/lib/python3.10/site-packages/sqlalchemy/sql/schema.py", line 950, in create
    bind._run_ddl_visitor(ddl.SchemaGenerator, self, checkfirst=checkfirst)
  File "/Users/tom/opt/anaconda3/envs/hc/lib/python3.10/site-packages/sqlalchemy/engine/base.py", line 2113, in _run_ddl_visitor
    visitorcallable(self.dialect, self, **kwargs).traverse_single(element)
  File "/Users/tom/opt/anaconda3/envs/hc/lib/python3.10/site-packages/sqlalchemy/sql/visitors.py", line 524, in traverse_single
    return meth(obj, **kw)
  File "/Users/tom/opt/anaconda3/envs/hc/lib/python3.10/site-packages/sqlalchemy/sql/ddl.py", line 890, in visit_table
    self.connection.execute(
  File "/Users/tom/opt/anaconda3/envs/hc/lib/python3.10/site-packages/sqlalchemy/engine/base.py", line 1289, in execute
    return meth(self, multiparams, params, _EMPTY_EXECUTION_OPTS)
  File "/Users/tom/opt/anaconda3/envs/hc/lib/python3.10/site-packages/sqlalchemy/sql/ddl.py", line 77, in _execute_on_connection
    return connection._execute_ddl(
  File "/Users/tom/opt/anaconda3/envs/hc/lib/python3.10/site-packages/sqlalchemy/engine/base.py", line 1378, in _execute_ddl
    compiled = ddl.compile(
  File "/Users/tom/opt/anaconda3/envs/hc/lib/python3.10/site-packages/sqlalchemy/sql/elements.py", line 491, in compile
    return self._compiler(dialect, **kw)
  File "/Users/tom/opt/anaconda3/envs/hc/lib/python3.10/site-packages/sqlalchemy/sql/ddl.py", line 29, in _compiler
    return dialect.ddl_compiler(dialect, self, **kw)
  File "/Users/tom/opt/anaconda3/envs/hc/lib/python3.10/site-packages/sqlalchemy/sql/compiler.py", line 451, in __init__
    self.string = self.process(self.statement, **compile_kwargs)
  File "/Users/tom/opt/anaconda3/envs/hc/lib/python3.10/site-packages/sqlalchemy/sql/compiler.py", line 486, in process
    return obj._compiler_dispatch(self, **kwargs)
  File "/Users/tom/opt/anaconda3/envs/hc/lib/python3.10/site-packages/sqlalchemy/sql/visitors.py", line 82, in _compiler_dispatch
    return meth(self, **kw)
  File "/Users/tom/opt/anaconda3/envs/hc/lib/python3.10/site-packages/sqlalchemy/sql/compiler.py", line 4332, in visit_create_table
    text += preparer.format_table(table) + " "
  File "/Users/tom/opt/anaconda3/envs/hc/lib/python3.10/site-packages/sqlalchemy/sql/compiler.py", line 5332, in format_table
    result = self.quote(name)
  File "/Users/tom/opt/anaconda3/envs/hc/lib/python3.10/site-packages/sqlalchemy/sql/compiler.py", line 5220, in quote
    if self._requires_quotes(ident):
  File "/Users/tom/opt/anaconda3/envs/hc/lib/python3.10/site-packages/sqlalchemy/sql/compiler.py", line 5129, in _requires_quotes
    or value[0] in self.illegal_initial_characters
IndexError: string index out of range

Feature Description

It'd be great to add clearer error handling to the .to_sql() method for cases like this (where name is empty by accident). I'm sure this has happened to other people, especially in testing frameworks and the like!

For example, even something very simple like this:

...
def to_sql(self, name, ...):
    if not name or name == "":
        raise ValueError("name parameter must be a non-empty string.")
...

could help quite a lot!

Alternative Solutions

I think this should be something that is pretty easy to handle with existing native python functionality, but I'm happy to clarify things further if people want 😄

Additional Context

No response

[ashton77]

Hey @tmccall8829 @debnathshoham
I'm a beginner here and trying to pick up this issue as my first. Some assistance here would really help.

Am I looking in the right place here ?

Thanks in advance!

[StefanieSenger]

take

[StefanieSenger]

Hey, I recreated the error message

engine = create_engine('sqlite:///:memory:', echo=False)
df = pd.DataFrame({'col1': [1, 2], 'col2': [3, 4]})
df.to_sql(name='', con=engine, if_exists='replace', index=False)

and added a ValueError to the SQLTable(PandasObject) class.

if not len(self.name):
    raise ValueError("Empty table name specified")

This seems to catch it. Curious if there's something to redo or improve. :)