迭代和组合列表中的元素

Question

I have a list:

li = ['a','b','c','d']

I want to iterate and combine iteratively the elements in the list such as the first one is combined to the 2nd one and go on. The final output I want is:

['a'],['a','b'],['a','b','c'],['a','b','c','d']

I tried using this way:

for i in range(0, len(li),i): 
    output = li[:i+i]
    print(output)

But I am getting only this result:

[]
['a', 'b', 'c', 'd']

Any idea where I am wrong and how to do this properly?

Answer 1

Your range values are incorrect, and i is undefined. This is a much simpler loop:

li = ['a','b','c','d']

for i in range(len(li)):
    output = li[:i+1]
    print(i, output)

Output:

0 ['a']
1 ['a', 'b']
2 ['a', 'b', 'c']
3 ['a', 'b', 'c', 'd']

Answer 2

You could modify the start and stop arguments in your use of range :

li = ['a', 'b', 'c', 'd']
for i in range(1, len(li) + 1):
    output = li[:i]
    print(output)

Output:

['a']
['a', 'b']
['a', 'b', 'c']
['a', 'b', 'c', 'd']