Python - how to store lines of numerical values?

I have a file with many lines each having over 20 numerical values, e.g.:

123 1 18 180776 4303656 1605 16468 0 51429 24230 0 0 0 4 8 0 8710 14705 1836 1 4 95
0 24538 0 187860 4264028 449 4711 0 2537 2537 0 0 5 0 0 0 6138 12880 1590 1 22 76
...

I'd like to:

1. read one line
2. save it in some python data type (what would be the best ?)
3. do some operations on each number taken from the above l开发者_开发知识库ine, e.g.:
   • check if it is not above sth (and save the result)
   • check if it is not belowe sth (and save the result)
   • count its length (number of digits) (and save the result)
   • compare it to the previous number from the same column
   -

So after a one line (with numbers) I should have:

1. store each number
2. store additional attributes for each number

Each number is compared to previous one from the same column, store the result but then I can forget the previous line.

What data type would be the best to store above data ?

Usually you would use a list for this

When you read a line into a variable, say row

row.split() 

will give you a list but each element will be a string, and you need numbers. You can get a list of numbers (looks like they are all integers) using a list comprehension like this

[int(x) for x in row.split()]

you can also use a list comprehension to compare with sth

This filters just the items that are < sth

[int(x) for x in row.split() if int(x)<sth]

This returns a list of bool where True means that the corresponding item is < sth

[int(x)<sth for x in row.split()]

It's hard to say which data type would be best without knowing what you're gonna do with the aggregated information. However, a simple solution would be to use a list for each line, containing 2-tuples with the actual number and a dictionary with attributes:

line = [(1, {'even': False, 'foo': 'bar'}), ..., (2332, {'even': True, 'foo': 'baz'}), ...]

Here's how to get this list starting from a line of text:

line = "4 0 2837 9323 ..."
line = [(int(n), dict()) for n in line.split()]

Then iterate the list and set attributes:

for n, attributes in line:
    ...
    attributes['foo'] = 'bar'

The standard data types should be fine for most purposes: i.e. list or tuple. Use list if you will be altering the values in-place.

You should be able to do something like this (untested code):

all_the_lines = []
with open("filename.txt", 'r') as f:
    for line in f:
        data = [int(x) for x in line.split()]
        # do something with the data if you want
        all_the_lines.append(data)

After this, all_the_lines will hold a list of lists with the raw data (converted to integers). You need to figure out how you will hold the other information you want to save: for example, pointers to all elements which were above a certain number. You can calculate all this during the loop above, or afterward.

If you want to perform heavy-duty mathematical calculations on the numbers (it sounds like you don't), consider using arrays from the numpy package instead.

Have a look at NumPy

• How to load an array
• How to test array values