CODEWITHSUNDEEP
python
user2840144
user2840144

Reputation: 173

Building multiple lists from single list with multiple lists within

def main():

    my_list = [[float(i) for i in line.split(',')] for line in open("Alpha.txt")]
    print(my_list)
    for elem in my_list:
        listA=[]
        listA = elem
        print(listA)


main()

this code prints out the correct data of which im looking for, however i need to set each print from the for loop into a object. Any help as to how i would go about doing that?

[1.2, 4.3, 7.0, 0.0]
[3.0, 5.0, 8.2, 9.0]
[4.0, 3.0, 8.0, 5.6]
[8.0, 4.0, 3.0, 7.4]

Upvotes: 0

Views: 70

Answers (3)

Ali
Ali

Reputation: 353

Try:

myList = [map(float, line.split(',')) for line in open ("Alpha.txt")]

Now you can get each line in a different variable if you want:

a = myList[0]
b = myList[1]

and so on. But since you have a list, it's better to use it and access elements using indices. Are you sure have a correct understanding of arrays?

As the other answers point out, it is dangerous and doesn't make sense to dynamically create variables.

Upvotes: 1

Sam van Kampen
Sam van Kampen

Reputation: 1013

This is not a good idea, let me warn you, and you should never use this in production code (it is prone to code injection), and screws up your global namespace, but it does what you asked.

You would use exec() for this, which is a function that dynamically executes statements.

def main():
    my_list = [[float(i) for i in line.split(',')] for line in open("Alpha.txt", "r")]
    print(my_list)
    for elem in my_list:
        exec "%s = %s" % ("abcdefghijklmnopqrstuvwxyz"[my_list.index(elem)], elem) in globals()

main()

Now, your global namespace is filled with variables a, b, c, etc. corresponding to the elements.

It is also prone to exceptions, if you have more than 26 elements, you will get an IndexError, although you could work around that.

Upvotes: 1

roippi
roippi

Reputation: 25954

What you're thinking of/trying to do is to dynamically name variables.

Don't.

Either leave your data in the list and access it via index

my_list[0] #what you were trying to assign to 'a'
my_list[0][0] #the first element in that sub-list

Or, if you have meaningful identifiers that you want to assign to each, you can use a dict to assign "keys" to "values".

d = {}
for sublist, meaningful_identifier in zip(my_list, my_meaningful_identifiers):
    d[meaningful_identifier] = sublist

Either way, leverage python data structures to do what they were supposed to do.

Upvotes: 2

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