Python 连接列表列表中的连续 True 值

Question

I have a list where each item is also a list. Each item contains some value and then a True or False value.

eg

list = [ 
['purple', False], 
['yellow', True], 
['red', True], 
['blue', False] 
['green', True], 
['orange', True], 
['black', True],
['cyan', False]
]

the desired output is to concatenate any True values that occur consecutively like so:

desired_list = [ 
['purple', False], 
['yellowred', True], 
['blue', False] 
['greenorangeblack', True], 
['cyan', False]
]

where, for example, 'yellow' and 'red' now both exist as a single string.

Thanks in advance for any help

Answer 1

Solution without itertools

data = [ 
['purple', False], 
['yellow', True], 
['red', True], 
['blue', False],
['green', True], 
['orange', True], 
['black', True],
['cyan', False]
]

out = []
prev = False
for i in data:
    if not prev or not i[1]:
        out.append(i)
    else:
        out[-1][0] += i[0]
    prev = i[1]

print(out)

[['purple', False], 
['yellowred', True], 
['blue', False], 
['greenorangeblack', True], 
['cyan', False]]

Answer 2

You can use groupby from the itertools package and a list comprehension to do this. Below groupby groups items of the list together by the last element of each item. The for-loop iterates over each grouping, merges the strings, and add the True/False.

from itertools import groupby

x = [ 
['purple', False], 
['yellow', True], 
['red', True], 
['blue', False],
['green', True], 
['orange', True], 
['black', True],
['cyan', False]
]


[[''.join(e[0] for e in g), k] for k, g in groupby(x, key=lambda x: x[-1])]
# returns:
[['purple', False],
 ['yellowred', True],
 ['blue', False],
 ['greenorangeblack', True],
 ['cyan', False]]

Answer 3

You can nicely solve it by recursion:

def compress(list_, i):
if i + 1 == len(list_):
    return
if list[i][1] and list[i+1][1]:
    list[i][0] += list[i+1][0]
    del list[i+1]
    compress(list_, i)
compress(list_, i + 1)

Answer 4

This doesn't create another list. It modifies the existing list.

list = [
['purple', False],
['yellow', True],
['red', True],
['blue', False],
['green', True],
['orange', True],
['black', True],
['cyan', False]
]

for item in list:
    i_now = list.index(item)
    if item[1]:
        while list[i_now+1][1]:
            item[0] = item[0] +'-'+ list[i_now+1][0]
            list.remove(list[i_now+1])
print(list)

Answer 5

Try using this function:

def get_concatenated(my_list):
    result = []
    concatenated_string = ''
    for i, item in enumerate(my_list):
        if item[1]:
            concatenated_string += item[0]

            # if last element is true
            if i == len(my_list) - 1:
                result.append([concatenated_string, True])

            continue

        if concatenated_string:
            result.append([concatenated_string, True])

        result.append(item)
        concatenated_string = ''

    return result