I have a tab-delimited file as below:
A 3 A 6
B 6 B 9
C 0 C 2
I wish to read the file in as below:
LIST = [['A', '3'], ['B', '6'], ['C', '0'], ['A', '6'], ['B', '9'], ['C', '2']]
The order is not important. I am only concerned that each row is read in increments of two and assigned to a sub list.
Any suggestions?
Thanks, S :-)
The most straightforward way would be:
>>> n = []
>>> for line in open(fname):
els = line.split('\t')
n.append(els[:2])
n.append(els[2:])
>>> n
[['A', '3'], ['A', '6'], ['B', '6'], ['B', '9'], ['C', '0'], ['C', '2']]
maybe slightly more efficient would be:
>>> g = (line.split('\t') for line in open(fname))
>>> [els[i:i+2] for els in g for i in range(0, 4, 2)]
[['A', '3'], ['A', '6'], ['B', '6'], ['B', '9'], ['C', '0'], ['C', '2']]
(0,2) instead of that range(0,4,2). Also if you do just split() (no arguments), it will split on space, tab, new lines... you can just do g = open(fname).read().split()This question actually allows for some Pythonic solutions.
l = open(fname).read().split()
LIST = zip(l[::2], l[1::2])
That's all there is to it. "Bam!"
Or we can "knock it up a notch":
def couple(i):
while True:
yield (i.next(), i.next())
LIST = [w for w in couple(iter(open(fname).read().split()))]
Additional benefits of those are that they will read the file in pairs, no matter if there are 4 columns (as in the example) or 6, 2... whatever
See also pythonic-way-to-split-comma-separated-numbers-into-pairs and how-do-you-split-a-list-into-evenly-sized-chunks-in-python
