lis = ["任务1", "任务2", "作者1", "作者2"]
# 根据lis内元素的前两个字符, 将lis分割为[["任务1", "任务2"], ["作者1", "作者2"]]

# 方法1
from itertools import groupby
result = [list(group) for key, group in groupby(sorted(lis), key=lambda x: x[:2])]

# 方法2
result = {}
for item in lis:
    key = item[:2]
    if key not in result:
        result[key] = []
    result[key].append(item)
result = list(result.values())