将多个返回值附加到Python中的不同列表

Question

I have function that calculates and returns 7 floats, and each value gets appended to a different list. I feel there must be something wrong if I am typing out 7 different append statements, but is there a more pythonic way todo this.

For example (I don't even like typing it here!):

a,b,c,d,e,f,g = range(7)
alist.append(a)
blist.append(b)
clist.append(c)
dlist.append(d)
elist.append(e)
flist.append(f)
glist.append(g)

According to this related question it would seem this is not possible... There must be a way using +=[a] or list comprehension or a loop or something?

One thing that comes to mind is to keep appending all those 7 values to a master list and then transpose it at the end with zip(*MasterList) to generate the individual lists?

What would people recommend?

Answer 1

appenders = range(7)
mylists = [alist, blist, clist, dlist, elist, flist, glist]
for x, lst in zip(appenders, mylists):
    lst.append(x)

Answer 2

Well one option is to create a list of arrays, for example, something like this:

    # define function like this:
    def range(7):
        ...
        return [a,b,c,d,e,f,g]

    # append to list:
    arr = range(7)
    arrList.append(arr)

    # How to call your variables:
    arrList[0][0]    # Should return first a.

You could make this option easier to work with, using dataframes from pandas , see this introduction , where you have to import pandas as pd ( as pd is recomended) and could define headers to your list:

    data = arrList    # You can use data = []
    columns = ['a', 'b', 'c', 'd', 'e', 'f', 'g']

    # Create the DataFrame
    df = DataFrame(data, columns)

    # And to add rows use*:
    df.append(range(7))

*See Documentation including DataFrame.Append()

Usage of this is the following:

    # Usage example:
    df['a']        # returns the alist
    df.loc[0,'a']  # returns first value in alist
    df.loc[0,:]    # returns row of values of all lists

And for more usage info, see this

A different option is creating a function that does all those appends in one bu you'll type the code anyway, like this:

    def range(n):
        ...
        return a,b,c,d,e,f,g

    def appendToLists(a,b,c,d,e,f,g):
        alist.append(a)
        blist.append(b)
        clist.append(c)
        dlist.append(d)
        elist.append(e)
        flist.append(f)
        glist.append(g)

    # Example:
    appendToLists(range(7))

Don't know if it's what your looking for because the list would have to be global.

Answer 3

Maybe you want a list of lists:

>>> [[item] for item in range(7)]
[[0], [1], [2], [3], [4], [5], [6]]

You could iterate over them without retyping the names.

Answer 4

I like @Ryne's answer because it is straightforward, but here is the option I am pondering.

# inside the loop
master_list.append(range(7))
# once you are done, transpose...
alist,blist,clist,dlist,elist,flist,glist = zip(*master_list)