Python: how to split a list into an unknown number of smaller lists based on a delimeter

I've got a list which contains the following strings:

MainList

'00:00'

'00:01'

'00:02'

'00:03'

'00:04'

'00:00'

'00:01'

'00:02'

'00:03'

'00:04'

I would like to split this into a smaller number of lists whenever '00:00' is encountered since '00:00' is the only element that won't change:

Desired output:

List1

'00:00'

'00:01'

'00:02'

'00:03'

'00:04'

List2

'00:00'

'00:01'

'00:02'

'00:03'

'00:04'

I tried looking at list slicing but the problem is that the last value and as such, number of elements may change. Moreover, I'm not sure how 开发者_如何转开发many smaller lists I'll need (and how I'd dynamically create n number of smaller lists?)

I usually do this:

def splitby( lst, breaker='00:00'):
    current = []
    it = iter(lst)
    first = next(it)
    assert first==breaker, "`lst` must begin with `breaker`"
    current.append(first)
    for item in it:
        if item == breaker:
            yield current
            current = []
        current.append(item)
    yield current

The inevitable itertools solution is a bit more general:

from itertools import groupby

class splitter(object):
    
    def __init__(self, breaker):
        self.breaker = breaker
        self.current_group = 0
        
    def __call__(self, item):
        if item == self.breaker:
            self.current_group+=1
        return self.current_group
        
    def group(self, items):
        return (list(v) for k,v in groupby(items,self))
    
print list(splitter('00:00').group(items))

In an explicit way, you could do like this :

sep = '00:00'
split_list = []
for item in Mainlist:
    if item == sep:
        split_list.append([item])
    else:
        split_list[-1].append(item)

print split_list

Comprehensions is your best friend :). Just two lines:

>>> a=['00:00', '00:01', '00:02', '00:03', '00:00', '00:01', '00:02']
>>> found=[index for index,item in enumerate(a) if item=='00:00'] + [len(a)]
>>> [a[found[i]:found[i+1]] for i in range(len(found)-1)]
[['00:00', '00:01', '00:02', '00:03'], ['00:00', '00:01', '00:02']]

Here is what we do:

We search for delimiter positions and get a list which contains delimiter indexes:

>>> found=[index for index,item in enumerate(a) if item=='00:00']
>>> found
[0, 4]

We're adding len(a) for including the last dict.

And creating new lists with splitting a with founded indexes :

>>> [a[found[i]:found[i+1]] for i in range(len(found)-1)]
[['00:00', '00:01', '00:02', '00:03'], ['00:00', '00:01', '00:02']]

I could think of another way :-)

def list_split(a):
    #a=['00:00', '00:01', '00:02', '00:03', '00:00', '00:01', '00:02']
    output = []
    count = 0

    if len(a) < 1:
        output.append(a)
        return output

    for i, item in enumerate(a[1:]):
        if item == a[0]:
            output.append(a[count:i+1])
            count = i + 1
    else:
        output.append(a[count:])
        return output