so I realize we are working on C# but I was wondering if someone can help me out with what should...

[G+_Jason Perry]

so I realize we are working on C# but I was wondering if someone can help me out with what should be a simple python question.

 

I want to clear out the data in a list after I am done using it.

 

for Line in RawFileList

    RawFileList[Line] = ""

 

I am using RawFileList to store the raw data from a file to be processed and spit out into another file.

[G+_Nate Follmer]

del RawFileList[:] <- This will clear the list completely. 

[G+_Lee Crocker]

Why do you think you need to clear the list? Just clear the variable:

 

RawFileList = []

 

This makes the variable point to an empty list, and the original list becomes unreferenced, and will be reclaimed by the garbage collector.

[G+_Jason Perry]

how do I just clear the variable?

RawFileList = ""

[G+_Lee Crocker]

That would do it too. As would "RawFileList = 5”, but using an empty list rather than a string or number seemed like the most lucid thing to do.

[G+_Jason Perry]

Well that seems to have done it.

 

Just for future reference am I going to run into any problems when I try to populate the variable again with a data file that has a different number of items or did that wipe out everything?

[G+_Lee Crocker]

It didn't "wipe out" anything. Variables are just names for things in Python--the things themselves exist independently. When you built up that list from a file, memory was allocated for all the values and the list made to point to them. Now the variable points to an empty list. The old list is still in memory, but since it has no name (no Python variable points to it) anymore, the garbage collector can reclaim that memory. Or it may decide not to until it needs the memory. That's what garbage collection is all about--you don't need to do the memory management yourself.

[G+_Jason Perry]

I am just so use to variables having fixed parameters that you just cant set the entire variable to nothing, I would have to set every entry to nothing, or let it decide what is in there.

[G+_Rik Schreurs]

Yes, it takes some getting used to, if you're coming from another language like C or Visual Basic. But this is really how Python works. If you have a list with things in it and you want to start over, the simplest way is to assign a new, empty list to that variable. (Like Lee said, it's just a name that refers to some object.)

 

Don't worry about cleaning stuff up, that's a job for the garbage collector.

[G+_Barry Fishman]

As others have said, you don't usually need to clear out things after you use them.  The garbage collector does that when the variable is no longer used, or when the variable is set to something else.

 

If you have some special need, such as wanting  to make sure data is no longer referenced, you can usually just set it to None.   Technically you can do:

 

del RawFileList

 

Which will cause an error to be signalled if your code uses the variable without giving it a new value.