Write a for loop on list of lists without changing the shape of the main list

[Antonio]

So I am new to python and am having difficulties on writing an efficient for loop on a list of lists. I have a list called "mylist" and I need to store the values of the first column of sublists, and for that I have written the following:

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newlist = [] for i in range(5):     for j in range(10):         d = [x for x in mylist[i][j][:,0]]         newlist.append(d)

The problem is the the answer I get is a list with "len = 50"; meanwhile I need to keep the shape of the "newlist" similar to "mylist" i.e. I want the final answer to be a list of 5 lists, and then in each list there should be 10 other lists. (Please see the attached files; I need to get something like "wanted_list"). I tried different things like:

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newlist = [] for i in range(5):     for j in range(10):         d[i] = [x for x in mylist[i][j][:,0]]         newlist.append(d)

or:

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newlist = [] for i in range(5):     for j in range(10):         d = [x for x in mylist[i][j][:,0]]     newlist.append(d)

But obviously non of these work. I was wondering if you could teach me how I can do this!

[gontajones]

When you access mylist[i][j] it returns the single item at that position.
Try something like this (if you really need to loop into every item):

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newlist = [] for i in range(len(mylist)):     d = []     for j in range(len(mylist[i])):         d.append(mylist[i][j])     newlist.append(d)

To get only the first item(column):

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newlist = [] for i in range(len(mylist)):     newlist.append([mylist[i][0]])

[Antonio]

When you access mylist[i][j] it returns the single item at that position.
Try something like this (if you really need to loop into every item):

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newlist = [] for i in range(len(mylist)):     d = []     for j in range(len(mylist[i])):         d.append(mylist[i][j])     newlist.append(d)

To get only the first item(column):

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newlist = [] for i in range(len(mylist)):     newlist.append([mylist[i][0]])

Thanks a bunch I got the idea now! :)

[ichabod801]

It's much better to loop over the items in the list than to loop of the indexes of the list:

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new_list = [] for sub_list in mylist:     new_list.append([])     for item in sub_list:         new_list[-1].append(item)