Check if an array is an element of another array python [duplicate]

Question

I have a python array of 3d points such as [p1,p2,...,pn] where p1 = [x1,y1,zi] I want to check weather a particular point p_i is a member of this, what is the right method for this?

Here is the code which I tried

import numpy
my_list = []
for x in range(0,10):
    for y in range(0,10):
        for z  in range(0,5):
            p1 = numpy.array([x,y,z])
            my_list.append(p1)

check_list = numpy.array([[1,2,3],[20,0,20],[5,5,5]])
for p in check_list :
    if p not in my_list:
        print (p)

However I;m getting the error

ValueError: The truth value of an array with more than one element is ambiguous. Use a.any() or a.all()

Apparently this method works for strings and numbers but not for arrays. What is the correct way to do this?

S P Sharan · Accepted Answer · 2021-08-16 14:34:09Z

1

import numpy

my_list = []
for x in range(0, 10):
    for y in range(0, 10):
        for z in range(0, 5):
            p1 = numpy.array([x, y, z])
            my_list.append(p1)

check_list = numpy.array([[1, 2, 3], [20, 0, 20], [5, 5, 5]])
for p in check_list:
    if not numpy.any(numpy.all(p == my_list, axis=1)):
        print(p)

answered Aug 16, 2021 at 14:34

S P Sharan

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Comments

not_speshal · Accepted Answer · 2021-08-16 14:35:02Z

1

Try using all along axis=1 and check if any of the result is True:

for p in check_list:
    if not (p==my_list).all(1).any():
        print(p)

Output:

[20  0 20]
[5 5 5]

edited Aug 16, 2021 at 14:35

answered Aug 16, 2021 at 14:29

not_speshal

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Comments

balderman · Accepted Answer · 2021-08-16 14:38:04Z

1

Give the below a try

from dataclasses import dataclass
from typing import List


@dataclass
class Point:
    x: int
    y: int
    z: int


points: List[Point] = []
for x in range(0, 10):
    for y in range(0, 10):
        for z in range(0, 5):
            points.append(Point(x, y, z))
print(Point(1, 2, 3) in points)
print(Point(1, 2, 3888) in points)

answered Aug 16, 2021 at 14:38

balderman

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2 Comments

brownser Over a year ago

Thank you for the suggestion, can you please tell me what exactly this one is doing? . points: List[Point] = [] ?

balderman Over a year ago

@brownfox I can tell you for sure :-). List[Point] is type hint. It increase the readability of the code and is used by type checkers. see docs.python.org/3/library/typing.html BTW - I think this solution is cleaner - it does not require any external lib!

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