Python *args AttributeError

Question

can anyone help me to figure out why the first code works and second dont?:

Working code

alias = []
alias.append(cx_Oracle.connect('%s/%s@%s' % (username, password, base)))
solve(*alias, **binds)

def solve(*alias, **binds):
    cur = alias[0].cursor()

Not working code

alias = []
alias.append(cx_Oracle.connect('%s/%s@%s' % (username, password, base)))
solve(alias, binds)

def solve(*alias, **binds):
    cur = alias[0].cursor()

Error

AttributeError: 'list' object has no attribute 'cursor'

*** Thanks all! That was very helpfull!

Answer 1

This is described in Keyword Arguments **binds, Arbitrary Argument Lists *alias and Unpacking Argument Lists solve(alias, binds) vs solve(*alias, **binds).

When you call solve(alias, binds), both arguments alias and binds are assigned to the formal parameter *alias.

This results in alias[0] being the list [ cx_Oracle.connect('%s/%s@%s' % (username, password, base)) ] instead of just the first element cx_Oracle.connect('%s/%s@%s' % (username, password, base)). And the list [...] doesn't have an attribute 'cursor', as Python aptly complains.