Find object in list that has attribute equal to some value (that meets any condition) Find object in list that has attribute equal to some value (that meets any condition) python python

Find object in list that has attribute equal to some value (that meets any condition)


next((x for x in test_list if x.value == value), None)

This gets the first item from the list that matches the condition, and returns None if no item matches. It's my preferred single-expression form.

However,

for x in test_list:    if x.value == value:        print("i found it!")        break

The naive loop-break version, is perfectly Pythonic -- it's concise, clear, and efficient. To make it match the behavior of the one-liner:

for x in test_list:    if x.value == value:        print("i found it!")        breakelse:    x = None

This will assign None to x if you don't break out of the loop.


Since it has not been mentioned just for completion.The good ol' filter to filter your to be filtered elements.

Functional programming ftw.

####### Set Up #######class X:    def __init__(self, val):        self.val = valelem = 5my_unfiltered_list = [X(1), X(2), X(3), X(4), X(5), X(5), X(6)]####### Set Up ########## Filter one liner ### filter(lambda x: condition(x), some_list)my_filter_iter = filter(lambda x: x.val == elem, my_unfiltered_list)### Returns a flippin' iterator at least in Python 3.5 and that's what I'm onprint(next(my_filter_iter).val)print(next(my_filter_iter).val)print(next(my_filter_iter).val)### [1, 2, 3, 4, 5, 5, 6] Will Return: #### 5# 5# Traceback (most recent call last):#   File "C:\Users\mousavin\workspace\Scripts\test.py", line 22, in <module>#     print(next(my_filter_iter).value)# StopIteration# You can do that None stuff or whatever at this point, if you don't like exceptions.

I know that generally in python list comprehensions are preferred or at leastthat is what I read, but I don't see the issue to be honest. Of course Python is not an FP language, but Map / Reduce / Filter are perfectly readable and are the most standard of standard use cases in functional programming.

So there you go. Know thy functional programming.

filter condition list

It won't get any easier than this:

next(filter(lambda x: x.val == value,  my_unfiltered_list)) # Optionally: next(..., None) or some other default value to prevent Exceptions


A simple example:We have the following array

li = [{"id":1,"name":"ronaldo"},{"id":2,"name":"messi"}]

Now, we want to find the object in the array that has id equal to 1

  1. Use method next with list comprehension
next(x for x in li if x["id"] == 1 )
  1. Use list comprehension and return first item
[x for x in li if x["id"] == 1 ][0]
  1. Custom Function
def find(arr , id):    for x in arr:        if x["id"] == id:            return xfind(li , 1)

Output all the above methods is {'id': 1, 'name': 'ronaldo'}


matomo