问题
In a list like the one below:
biglist = ['X', '1498393178', '1|Y', '15496686585007',
'-82', '-80', '-80', '3', '3', '2', '|Y', '145292534176372',
'-87', '-85', '-85', '3', '3', '2', '|Y', '11098646289856',
'-91', '-88', '-89', '3', '3', '2', '|Y', '35521515162112',
'-82', '-74', '-79', '3', '3', '2', '|Z',
'0.0', '0.0', '0', '0', '0', '0', '0', '4', '0', '154']
There could be some numerical elements preceded by a character. I would like to break this into sub-lists like below:
smallerlist = [
['X', '1498393', '1'],
['Y', '1549668', '-82', '-80', '-80', '3', '3', '2', ''],
['Y', '1452925', '-87', '-85', '-85', '3', '3', '2', ''],
['Y', '3552151', '-82', '-74', '-79', '3', '3', '2', ''],
['Z', '0.0', '0.0', '0', '0', '0', '0', '0', '4', '0', '154']
]
As you can tell, depending upon the character, the lists could look similar. Otherwise they could have a different number of elements, or dissimilar elements altogether. The main separator is the "|" character. I have tried to run the following code to split up the list, but all I get is the same, larger, list within a list. I.e., list of len(list) == 1.
import itertools
delim = '|'
smallerlist = [list(y) for x, y in itertools.groupby(biglist, lambda z: z == delim)
if not x]
Any ideas how to split it up successfully?
回答1:
First, a quick oneliner, which is not an optimal solution in terms of space requirements, but it's short and sweet:
>>> smallerlist = [l.split(',') for l in ','.join(biglist).split('|')]
>>> smallerlist
[['X', '1498393178', '1'],
['Y', '15496686585007', '-82', '-80', '-80', '3', '3', '2', ''],
['Y', '145292534176372', '-87', '-85', '-85', '3', '3', '2', ''],
['Y', '11098646289856', '-91', '-88', '-89', '3', '3', '2', ''],
['Y', '35521515162112', '-82', '-74', '-79', '3', '3', '2', ''],
['Z', '0.0', '0.0', '0', '0', '0', '0', '0', '4', '0', '154']]
Here we join all elements of the big list by a unique non-appearing separator, for example ,, then split by |, and then split again each list into a sublist of the original elements.
But if you're looking for a bit more efficient solution, you can do it with itertools.groupby that will operate on an intermediate list, generated on fly with the breakby() generator, in which elements without | separator are returned as is, and those with separator are split into 3 elements: first part, a list-delimiter (e.g. None), and the second part.
from itertools import groupby
def breakby(biglist, sep, delim=None):
for item in biglist:
p = item.split(sep)
yield p[0]
if len(p) > 1:
yield delim
yield p[1]
smallerlist = [list(g) for k,g in groupby(breakby(biglist, '|', None),
lambda x: x is not None) if k]
回答2:
It would be easier to join the elements of the list into a single string, split the string on the '|' character, then split each of those elements on the what you used to join the list. Probably a comma ,
bigstr = ','.join(biglist)
[line.split(',') for line in bigstr.split('|')]
# returns
[['X', '1498393178', '1'],
['Y', '15496686585007', '-82', '-80', '-80', '3', '3', '2', ''],
['Y', '145292534176372', '-87', '-85', '-85', '3', '3', '2', ''],
['Y', '11098646289856', '-91', '-88', '-89', '3', '3', '2', ''],
['Y', '35521515162112', '-82', '-74', '-79', '3', '3', '2', ''],
['Z', '0.0', '0.0', '0', '0', '0', '0', '0', '4', '0', '154']]
If the list is very long, you can also iterate over the items in the list, creating a new sublists on when you encounter a pipe character |
new_biglist = []
sub_list = []
for item in biglist:
if '|' in item:
end, start = item.split('|')
sub_list.append(end)
new_biglist.append(sub_list)
sub_list = [start]
else:
sub_list.append(item)
new_biglist
# return:
[['X', '1498393178', '1'],
['Y', '15496686585007', '-82', '-80', '-80', '3', '3', '2', ''],
['Y', '145292534176372', '-87', '-85', '-85', '3', '3', '2', ''],
['Y', '11098646289856', '-91', '-88', '-89', '3', '3', '2', ''],
['Y', '35521515162112', '-82', '-74', '-79', '3', '3', '2', '']]
回答3:
Here is a solution to a similar problem I didn't find an answer to. How to split a list into sublists delimited by a member, e.g. character:
l = ['r', 'g', 'b', ':',
'D', 'E', 'A', 'D', '/',
'B', 'E', 'E', 'F', '/',
'C', 'A', 'F', 'E']
def split_list(thelist, delimiters):
''' Split a list into sub lists, depending on a delimiter.
delimiters - item or tuple of item
'''
results = []
sublist = []
for item in thelist:
if item in delimiters:
results.append(sublist) # old one
sublist = [] # new one
else:
sublist.append(item)
if sublist: # last bit
results.append(sublist)
return results
print(
split_list(l, (':', '/'))
)
# => [['r', 'g', 'b'], ['D', 'E', 'A', 'D'],
# ['B', 'E', 'E', 'F'],
# ['C', 'A', 'F', 'E']]
回答4:
You don't need regex or anything of the sort - a simple loop and str.split() should be more than enough, at least if you're after an actual efficient solution:
biglist = ['X', '1498393178', '1|Y', '15496686585007', '-82', '-80', '-80', '3', '3', '2',
'|Y', '145292534176372', '-87', '-85', '-85', '3', '3', '2', '|Y',
'11098646289856', '-91', '-88', '-89', '3', '3', '2', '|Y', '35521515162112',
'-82', '-74', '-79', '3', '3', '2', '|Z', '0.0', '0.0', '0', '0', '0', '0',
'0', '4', '0', '154']
delimiter = "|"
smaller_list = [[]]
for x in biglist:
if delimiter in x:
a, b = x.split(delimiter)
if a: # remove the check if you also want the empty elements
smaller_list[-1].append(a)
smaller_list.append([])
if b: # remove the check if you also want the empty elements
smaller_list[-1].append(b)
else:
smaller_list[-1].append(x)
print(smaller_list)
# [['X', '1498393178', '1'],
# ['Y', '15496686585007', '-82', '-80', '-80', '3', '3', '2'],
# ['Y', '145292534176372', '-87', '-85', '-85', '3', '3', '2'],
# ['Y', '11098646289856', '-91', '-88', '-89', '3', '3', '2'],
# ['Y', '35521515162112', '-82', '-74', '-79', '3', '3', '2'],
# ['Z', '0.0', '0.0', '0', '0', '0', '0', '0', '4', '0', '154']]
来源：https://stackoverflow.com/questions/45281189/split-list-into-lists-based-on-a-character-occurring-inside-of-an-element