Question

I am trying to parse some SQL statements (CREATE TABLE exactly) using pyparsing. For both database name and table table I have created identifiers:

identifier = (Combine(Optional('"') + Word(alphanums) + 
                      ZeroOrMore('_' + Word(alphanums)) + 
                      Optional('"')) & ~keywords_set)

database_name = identifier.setResultsName('database_name')
table_name = identifier.setResultsName('table_name')

I am also using this parsing method:

def parse(self, sql):
    try:
        tokens = self.create_table_stmt.parseString(sql)
        print tokens.database_name, tokens.table_name
        values = tokens.database_name, tokens.table_name
        print values
        return values
    except ParseException as error:
        print error

For following input:

    CreateTableParser().parse('''
CREATE TABLE "django"."django_site1" (
)''')

i get:

['"django"'] ['"django_site1"']
((['"django"'], {}), (['"django_site1"'], {}))

Why these are different? How can I just get the output in the first way, as simple lists? I only get it when I print those values.

Answer 1

There is a difference between print a, b and print (a,b):

>>> a, b = "ab"
>>> a
'a'
>>> b
'b'
>>> print a, b
a b
>>> print (a, b)
('a', 'b')

print a, b prints two objects a and b. print (a, b) prints a single object the tuple a, b:

>>> w = sys.stdout.write
>>> _ = w(str(a)), w(' '), w(str(b)), w('\n')
a b
>>> _ = w(str((a,b))), w('\n')
('a', 'b')

Or to put it another way:

>>> class A:
...    def __str__(self):
...        return '1'
...    def __repr__(self):
...        return 'A()'
... 
>>> print A(), A()
1 1
>>> print (A(), A())
(A(), A())

__str__ method is called when you do str(obj). If there is no __str__ method then __repr__ method is called repr(obj).