how to decrease the value of items in a list python-CodePudding

I wanted to find similar items in a list with slightly lower or higher values (0.01 or -0.01) but up to 0.1, example:

real_list = [1.94, 4.72, 8.99, 5.37, 1.33]
list_2 = [1.86, 4.78, 8.91, 5.41, 1.30]

you can see that the values of the two lists are similar, but they are not found in an if, example:



for i in list_2:
    if i in real_list:
        print("found")
    else:
        print("not found")

this code returns me this

not found
not found
not found
not found
not found

I tried to make some modifications but I wanted it to do some combinations decreasing and increasing values in different parts until it found the value in the other list, example:

list_2 = [1.86, 4.78, 8.91, 5.41, 1.30]
1.85
4.77
8.9
5.4
1.29
1.84
4.76

or increase the values until you find it in the list, remembering that it has to be close to 0.1 and nothing more, in short is to find similar values in a list.

Can someone help me?

CodePudding user response：

You need to be sure what you mean when two values are "similar". If I understand you correctly you set an arbitrary threshold of 0.1, for this the code could look something like this:

real_list = [1.94, 4.72, 8.99, 5.37, 1.33]
list_2 = [1.86, 4.78, 8.91, 5.41, 1.30]
threshold = 0.1
for i in list_2:
  found = False
  for j in real_list:
    if abs(i-j) <= threshold:
      print("found")
      found = True
      break
  if not found:
    print("not found")

CodePudding user response：

with a bit of numpy this becomes a rather compact

import numpy as np
real_list = np.array([1.94, 4.72, 8.99, 5.37, 1.33])
list_2 = [1.86, 4.78, 8.91, 5.41, 1.30]
["found" if  np.any(np.isclose(x,real_list,atol=0.04)) else "not found"  for x in list_2]

np.isclose(x,real_list,atol=0.04) does the comparison of each value in list_2 against the whole vector with a given tolerance - can be atol = absolute tolerance and/or rtol: relative tolerance (https://numpy.org/doc/stable/reference/generated/numpy.isclose.html).

np.any then reduces the comparison of each value into a single boolean.

CodePudding user response：

You can do something like this:

real_list = [1.94, 4.72, 8.99, 5.37, 1.33]
list_2 = [1.86, 4.78, 8.91, 5.41, 1.30]

for x in real_list:
    for y in list_2:

        if abs(x-y)<0.1:
            print("found",x, "is close to",y)
        else:
            print("not found")

It will run all the itens in your first list, and all itens in your second list and compare if they are less than 0.1 away from eachother.