How can I get specific elements from a tuple/list in Python without iterating?

[Punkyc7]

I am using python to get tuples from a db.

I am doing

cur.execute("Select Statement");

I use cur.fetchall to get the tuples.

My question is how do you iterate over the returned tuples and store the columns into an array? I want to iterate over n tuples, not all the returned results. Is storing the results into an array necessary or is the returned tuple considered an or a list?


Thanks for the help!

 

[Dick]

I am using python to get tuples from a db.

I am doing

cur.execute("Select Statement");

I use cur.fetchall to get the tuples.

My question is how do you iterate over the returned tuples and store the columns into an array? I want to iterate over n tuples, not all the returned results. Is storing the results into an array necessary or is the returned tuple considered an or a list?


Thanks for the help!

The only real difference betwen a tuple and a list is that tuples are not mutable (changeable). Lists are. They are both iterable. If you really want to change them you can change a tuple t into a list l with l=list(t).

 

[Punkyc7]

Ok so if the select statement returns 50 tuples that are of type (int, String) and say I only wanted 5 of them, would I have to iterate over the cur or Is there a way to just get the first 5?

Sorry if this is a stupid question, I am just getting into python.

 

[Dick]

Ok so if the select statement returns 50 tuples that are of type (int, String) and say I only wanted 5 of them, would I have to iterate over the cur or Is there a way to just get the first 5?

Sorry if this is a stupid question, I am just getting into python.

It's not stupid. No, to get the first five elements of a tuple/list t into a tuple/list s, say s=t[:5]. Look up the way Python handles subrange indexing. It's really quite neat. You don't have to iterate to do something like that.

 

[LudusRex]

There are a few different ways to get specific elements from a tuple or list in Python without iterating. One option is to use indexing, where you can access a specific element by its index number. For example, if you have a tuple called "tup" with three elements, you can get the second element by using "tup[1]". This method can also be used for lists.

Another option is to use the unpacking operator, which allows you to assign multiple variables at once based on the elements in a tuple or list. For example, if you have a tuple called "tup" with three elements, you can do "a, b, c = tup" and this will assign the first element to variable "a", the second element to variable "b", and the third element to variable "c".

In your specific case, since you are using Python to get tuples from a database, you can use the cursor object's "fetchone()" method to get a single tuple at a time, without iterating through all the results. This method will return a tuple, which you can then use indexing or unpacking to get specific elements from.

As for storing the columns into an array, it depends on your specific needs and what you plan to do with the data. If you only need to access the data once and in a specific order, then storing it into an array may not be necessary. However, if you need to manipulate or access the data multiple times, then storing it into an array could be useful. The returned tuple is considered a tuple, not a list, but you can easily convert it to a list if needed by using the "list()" function.