def func(bar):
my_dict = {
'query1': 'select * from table1',
'query2': 'select * from table2'
}
my_dict[bar]
func('query1')
My question is does my_dict executes both query and save it or it only executes query according to bar variable
In this specific case, no query are executed at all. It is only str objects which means that they actually don't do anything.
Let's try to detail 2 other cases. Assuming you have a function execute_query that execute a query given as parameter:
def func(query):
my_dict = {
'query1': execute_query('select * from table1'),
'query2': execute_query('select * from table2'),
}
return my_dict[query]
func('query1')
In this case, both query will be executed because Python interpreter will analyse the dictionary composition. On the other hand, if you have a reference to this function, it won't call the function. Example:
def do_query1():
return execute_query('select * from table1')
def do_query2():
return execute_query('select * from table2')
def func(query):
my_dict = {
'query1': do_query1,
'query2': do_query2,
}
return my_dict[query]() # <-- appropriate function will be call here
func('query1')
That will create the dictionary with two elements in memory, find the value associated with key bar and destroy the whole thing when the function is competed.
my_dictifbaris one of the keys of the same dictionary...