在附加到列表时应用 lambda function

Question

Imagine a one dimensional array 'inter' and an empty list 'visual_pred'. I want to iterate over all elements in the array and append each element to my list while adding the element with the list's last entry.

My code looks like this:

visual = []

for x in inter:
    if x > 0:
        visual.append(lambda x: x + visual[-1])
    else:
        visual.append(visual[-1])

After executing the code all entries in my list 'inter' looks like this:

 function __main__.lambda(x)

What is the problem here and how can I challenge it?

Answer 1

What you're doing here is appending the lambda function itself to your list and not the lambda functions output.I don't actually see why you need a lambda here anyway. This does what you want.

visual = []

for x in inter:
    if x > 0:
        visual.append(x + visual[-1])
    else:
        visual.append(visual[-1])

Answer 2

As BeanBagTheCat pointed out, you're appending the lambda function itself to your list and not the lambda functions output. You can write the same code by BeanBagTheCat in one line using list-comprehension as follows:

visual = [x + visual[-1] if x > 0 else visual[-1] for x in inter]