Convert lists into 'transposed' list

Question

This is probably a beginners question but I don't know how to search for an answer (because I cannot "name" the question)

I have 2 lists or a tuple of 2 lists

xxx = ["time1", "time2", "time3"]
yyy = ["value1", "value2", "value3"]
zzz=(xxx,yyy)

now I would like to create a list/tuple for every entry result should be

[['time1', 'value1'], ['time2', 'value2'], ['time3', 'value3']]

I'm able to do this with a for loop (and zip) but is there no "nicer" solution? Here is a similar question but I'm not able to use the resolution given there for my probelms

Answer 1

Use the builtin zip function:

 zzz = zip(xxx, yyy) 

Of course, this creates a list of tuples (or an iterable of tuples in python3.x). If you really want a list of lists:

 #list (python2.x) or iterable(python3.x) of lists
 zzz = map(list,zip(xxx,yyy)) 

or

 #list of lists, not list of tuples
 #python 2.x and python 3.x
 zzz = [ list(x) for x in zip(xxx,yyy) ]

If you're using python3.x and you want to make sure that zzz is a list, the list comprehsion solution will work, or you can construct a list from the iterable that zip produces:

#list of tuples in python3.x.  
zzz = list(zip(xxx,yyy)) #equivalent to zip(xxx,yyy) in python2.x
                         #will work in python2.x, but will make an extra copy.
                         # which will be available for garbage collection
                         # immediately

Answer 2

I notice that your data includes time stamps and numbers. If you're doing number-intensive calculations, then numpy arrays might be worth a look. They offer better performance, and transposing is very simple. ( arrayname.transpose() or even arrayname.T )