parsing a python string with floats and ints

Question

I have hundreds of string that all have the same format -- 2 integers followed by three floats. An example:

1 10 1.2345 5.4321 10.5647

I just want to take these strings one-by-one and parse them into their respective ints and floats. I can think of a few ways to do this, but I was hoping that python would have something elegant, kind of an inverse of the str.format thing that gets used for writing. This seems like very basic functionality, so I'm sorry if I am asking something that has been answered, but I can't find a solution anywhere. Any thoughts? Thanks.

Heh, they don't want you to try too hard, I guess? It starts: "If you’re a developer and you’re about to ask another developer a technical question (on a forum, via email, on a chat channel, or in person), you’d better be ready to answer the question “What have you tried?”" — askewchan
– askewchan, Commented Mar 11, 2013 at 21:41

voithos · Accepted Answer · 2013-03-11 21:10:49Z

4

A simple list comprehension should do the trick

>>> mystr = '1 10 1.2345 5.4321 10.5647'
>>> [int(s) if s.isdigit() else float(s) for s in mystr.split()]
[1, 10, 1.2345, 5.4321, 10.5647]

answered Mar 11, 2013 at 21:10

voithos

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1 Comment

DSM Over a year ago

This would convert negative integers to floats. Probably that wouldn't be an issue, but ast.literal_eval would avoid it.

askewchan · Accepted Answer · 2013-03-11 21:36:11Z

2

I think you'd be best off with something like numpy's genfromtxt or loadtxt:

import numpy as np
import StringIO

s = """1 10 1.2345 5.4321 10.5647
       2 14 434.35 345.34 1000000
       3 8  253.235 2.53 .002345"""
f = StringIO.StringIO(s)

data = np.genfromtxt(f, names = 'id, count, x, y, z', dtype=[int,int,float,float,float])

This gives you an array of these things, so the first row is accessible as

data[0]
#(1, 10, 1.2345, 5.4321, 10.5647)

Or all the second column:

data['count']
#array([10, 14,  8])

By the way, this will convert an integer in the float column into a float, in case one of your floats happens to be an integer.

edited Mar 11, 2013 at 21:36

answered Mar 11, 2013 at 21:21

askewchan

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Comments

dawg · Accepted Answer · 2013-03-11 21:52:33Z

1

You could do something like this:

def linep(line):
    line=line.split()
    try:
        ints=map(int, line[0:2])
        floats=map(float, line[2:5])
    except ValueError as e:
        print e
    return ints+floats

print linep('1 10 1.2345 5.4321 10.5647')

Then use it this way:

>>> s='''1 10 1.2345 5.4321 10.5647
 -2 11 -0.5 0.5 .3'''
>>> for line in s.splitlines():
...     print linep(line)

Prints:

[1, 10, 1.2345, 5.4321, 10.5647]
[-2, 11, -0.5, 0.5, 0.3]

edited Mar 11, 2013 at 21:52

answered Mar 11, 2013 at 21:44

dawg

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1 Comment

bob.sacamento Over a year ago

Thanks. Something like that was one of my options. I was hoping for something short and sweet, though, kind of like formatted output in reverse.

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