Trying to input data from a txt file in a list, then make a list, then assign values to the lines

Question

allt = []
with open('towers1.txt','r') as f:   
    towers = [line.strip('\n') for line in f]
    for i in towers:
        allt.append(i.split('\t'))
    print allt [0]

now i need help, im inputting this text

mw91 42.927 -72.84 2.8
yu9x 42.615 -72.58 2.3
HB90 42.382 -72.679 2.4

and when i output im getting

['mw91 42.927 -72.84 2.8']

where in my code and what functions can i use to define the 1st 2nd 3rd and 4th values in this list and all the ones below that will output, im trying

allt[0][2] or 
allt[i][2] 

but that dosent give me -72.84, its an error, then other times it goes list has no attribute split

update, maybe i need to use enumerate?? i need to make sure though the middle 2 values im imputing though can be used and numbers and not strings because im subtracting them with math

Answer 1

Are you sure those are tabs? You can specify no argument for split and it automatically splits on whitespace (which means you won't have to strip newlines beforehand either). I copied your sample into a file and got it to work like this:

allt = []
with open('towers1.txt','r') as f:   
   for line in f:
        allt.append(line.split())

>>>print allt[0]
['mw91', '42.927', '-72.84', '2.8']
>>>print allt[0][1]
'42.927'

Footnote: if you get rid of your first list comprehension, you're only iterating the file once, which is less wasteful.

---

Just saw that you want help converting the float values as well. Assuming that line.split() splits up the data correctly, something like the following should probably work:

allt = []
with open('towers1.txt','r') as f:   
   for line in f:
         first, *_else = line.split() #Python3
         data = [first]
         float_nums = [float(x) for x in _else]
         data.extend(float_nums)
         allt.append(data)

>>>print allt[0]
['mw91', 42.927, -72.84, 2.8]

For Python2, substitute the first, *_else = line.split() with the following:

first, _else = line.split()[0], line.split()[1:]

---

Finally (in response to comments below), if you want a list of a certain set of values, you're going to have to iterate again and this is where list comprehensions can be useful. If you want the [2] index value for each element in allt , you'll have to do something like this:

 >>> some_items = [item[2] for item in allt]
 >>> some_items
 [-72.84, -72.58, -72.679]

Answer 2

[] implies a list.

'' implies a string.

allt = ['mw91 42.927 -72.84 2.8']

allt is a list that contains a string:

allt[0] --> 'mw91 42.927 -72.84 2.8'

allt[0][2] --> '9'

allt.split() --> ['mw91', '42.927', '-72.84', '2.8']

allt.split()[2] --> '-72.84' #This is still a string.

float(allt.split()[2]) --> -72.84 #This is now a float.

Answer 3

I think this should also work

with open('towers.txt', 'r') as f:
    allt = map(str.split, f)

And if you need the values after the first one to be floats...

with open('towers.txt', 'r') as f:
    allt = [line[:1] + map(float, line[1:]) for line in map(str.split, f)]