is_snake_case_file_name

stringtools.is_snake_case_file_name(expr)

Is true when expr is a string and is underscore-delimited lowercase file name with extension.

>>> stringtools.is_snake_case_file_name('foo_bar')
True

Otherwise false:

>>> stringtools.is_snake_case_file_name('foo.bar.blah')
False

Returns true or false.