Making list that takes in value if value appears more than once-CodePudding

If my list has values that appears more than once I want to do the following:

my_list = ['a','b','c','a','a','b']

I want that my_list becomes ['a','b','c']
and at the same time new_list = ['a','a','b']

I have started with the code but can't manage to finish it:

def func(word):
    tgt = 1
    found = []
    lst = [1,2,3,45,6,1]
    if lst.count(word)> 1:
        found.append(word)
    return found, lst
print(func(1))

CodePudding user response：

You can iterate through the list, store the element in one list if it is not visited or in a new list if it is already visited:

my_list = ['a','b','c','a','a','b']
visited, lst, new_list = set(), [], []
for x in my_list:
    if x not in visited:
        lst.append(x)
        visited.add(x)
    else:
         new_list.append(x)
         
print(lst, new_list)
# ['a', 'b', 'c'] ['a', 'a', 'b']

CodePudding user response：

my_list = ['a','b','c','a','a','b']
new_list = my_list.copy()

my_list = list(set(my_list))
my_list.sort()

# remove unique items from new_list
for item in my_list:
    new_list.pop(new_list.index(item))

CodePudding user response：

I'm going to use a collections.Counter() to count up the occurrences of each items in the list. At that point the keys() become your new my_list and then we will use some list multiplication to construct your new_list.

import collections
data = ['a','b','c','a','a','b']
counted = collections.Counter(data)

At this point finding your new my_list is dead simple:

my_list  = list(counted)
print(my_list)

gives you:

['a', 'b', 'c']

Now we can leverage the fact that ['a'] * 4 == ['a', 'a', 'a', 'a'] to construct a list from they keys of counted based on the number of times they were identified.

new_list = []
for key, value in counted.items():
    if value > 1:
        new_list.extend([key]*(value-1))
print(new_list)

This will give us back:

['a', 'a', 'b']

Full Solution:

import collections
data = ['a','b','c','a','a','b']
counted = collections.Counter(data)

my_list  = list(counted)
new_list = []
for key, value in counted.items():
    if value > 1:
        new_list.extend([key]*(value-1))

print(my_list, new_list)

CodePudding user response：

lst = ["a","b","a","c","d","b"]
new_list=[]
for i in lst:
    if i not in new_list: # check the new list if values repeat or not
        new_list.append(i) # add the repeating values in new list
for i in new_list: 
    if i in lst: 
        lst.remove(i) # remove the repeating values from first list
print(lst,new_list)

at first you can add the repeating values in a different list then remove these values from your first list.

CodePudding user response：

  l = ['a', 'b', 'c', 'a', 'c']
  arr = []
  for x in l:
      if x not in a:
          arr.append(x)
  # now arr only have the non repeating elements of the array l