CODEWITHSUNDEEP
pythonlist
Small_J
Small_J

Reputation: 43

How to eliminate items in the list of python

I have a list in python:

A=[[303  80]
   [390  43]
   [446  16]
   [471  16]
   [505  44]
   [557 225]
   [642  22]
   [672  15]
   [694  86]
   [702  76]]

Now I want to remove the rows A[i] which have a bigger summary value than the next item in the list.

A[i][0]+A[i][1] > A[i+1][0]

I code this lines:

B=[]
for i in range(len(A)-1):
  if A[i][0]+A[i][1]<=A[i+1][0]:
      B.append(A[i])
B.append(A[i+1])

I got this result:

B=[[303  80]
   [390  43]
   [446  16]
   [471  16]
   [505  44]
   [642  22]
   [672  15]
   [702  76]]

Are there any other ways which are shorter and quicker than this. Thank you very much.

Upvotes: 0

Views: 98

Answers (4)

Sunitha
Sunitha

Reputation: 12015

[a for a,b in zip(A, A[1:]) if sum(a)<=b[0]] + [A[-1]]

or

[a for i,a in enumerate(A[:-1]) if sum(a)<=A[i+1][0]] + [A[-1]]

Upvotes: 2

Mateen Ulhaq
Mateen Ulhaq

Reputation: 27201

Iterate through a zip of (current, next) items.

def filt(A):
    def cond(a, b):
        return a[0] + a[1] <= b[0]

    return [a for a, b in zip(A, A[1:]) if cond(a, b)] + [A[-1]]

You might even consider itertools, or better, numpy if performance is an issue.

NOTE: This solution falls for the problems I discussed in a comment above.

As @smci mentions, doing this naively like this might give you something you weren't expecting. filt(A) is not the same as filt(filt(A)) for all possible inputs A.

Upvotes: 2

Paula Thomas
Paula Thomas

Reputation: 1190

Try:

B=[d  for c,d in enumerate(A) if c < len(A)-1 and A[c][0]+A[c][1] <= A[c+1][0]]
B.append(A[-1])

Upvotes: 0

Taohidul Islam
Taohidul Islam

Reputation: 5414

You can use list comprehension for an one-liner solution.

Without last element (because last element has no next element to compare):

expected_list = [A[i] for i in range(len(A)-1) if A[i][0] + A[i][1] <= A[i + 1][0]]

With Last element (your expected output):

expected_list = [A[i] for i in range(len(A)) if i==len(A)-1 or A[i][0] + A[i][1] <= A[i + 1][0]]

Upvotes: 0

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