CODEWITHSUNDEEP
pythonlist
R. Trading
R. Trading

Reputation: 165

How do I remove these values in a list in Python?

x1 = [1, 2, 3, 4, 5, 6]
x2 = [3, 5, 6, 8, 9]
x3 = [2, 4, 5, 7, 13]
x4 = [11, 22, 33, 24, 55, 66]
x5 = [11, 7, 1, 2, 3, 4, 5, 6]

How do I remove the increasing values on every list?

If I removed the increasing in those lists, they should look like this:

x1 = [1, 6]
x2 = [3, 9]
x3 = [2, 13]
x4 = [11, 33, 24, 66]
x5 = [11, 7, 1, 6]

Upvotes: 0

Views: 45

Answers (3)

AChampion
AChampion

Reputation: 30258

You can use a generator to build up the runs and yield the results, e.g.:

def runs(iterable):
    iterable = iter(iterable)
    i = [next(iterable)]  # Empty iterable not handled
    for j in iterable:
        while j and i[-1] < j:
            i.append(j)
            j = next(iterable, None)
        i[1:-1] = []      # Removes the middle of the run, if there is one
        yield from i
        i = [j]
    if j:
        yield j

# Using @StephenRauch data set
data = (
    [1, 2, 3, 4, 5, 6],
    [3, 5, 6, 8, 9],
    [2, 4, 5, 7, 13],
    [11, 22, 33, 24, 55, 66],
    [11, 7, 1, 2, 3, 4, 5, 6]
)

>>> [list(runs(d)) for d in data]
[[1, 6], [3, 9], [2, 13], [11, 33, 24, 66], [11, 7, 1, 6]]

Upvotes: 2

Stephen Rauch
Stephen Rauch

Reputation: 49794

This will remove any increasing elements:

Code:

def remove_increasing(a_list):
    return [a_list[0]] + \
           [y for x, y in zip(a_list, a_list[1:]) if x >= y] + \
           [a_list[-1]]

Test Code:

data = (
    [1, 2, 3, 4, 5, 6],
    [3, 5, 6, 8, 9],
    [2, 4, 5, 7, 13],
    [11, 22, 33, 24, 55, 66],
    [11, 7, 1, 2, 3, 4, 5, 6]
)

for d in data:
    print(remove_increasing(d))

Results:

[1, 6]
[3, 9]
[2, 13]
[11, 24, 66]
[11, 7, 1, 6]

Upvotes: 1

John Gordon
John Gordon

Reputation: 33335

Your question is unclear. What does "remove the increasing values" mean?

Clearly you don't mean "remove every value that is larger than the previous one", because your example results include the last element which is larger.

But, assuming you know what you mean, here's how to do it:

To delete a value from a list:

mylist.remove(4)

To remove the item at a specific position from a list: (remember that Python lists start at position zero, not position one)

del mylist[2]

Upvotes: 0

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