How to return True and false if duplicate value exists

Question

I have a list:

list = ["A", "A", "B", "A", "C"]

and a for and if statement combined:

for x in list:
    if "A" in x:
        print("true")

Output for the above code:

true
true

Next, I am figuring out how to tell me there is duplicates of "A" in list and return me value of True

Here is what i have tried:

for x in list:
    if any(x == "A" in x):
        return True

but an error shows up: SyntaxError: 'return' outside function

tried this too:

 for x in list:
    if any(x == "A" in x):
    return True
SyntaxError: expected an indented block

my desired output would be:

True because duplicates of "A" exists

`return` statements are to be used in functions. And in your second attempt, the error is quite selfexplanatory — yatu, Oct 18 '19 at 07:51
Python needs indented code in order to work. You just have to shift a couple of spaces to the right the code "return True", and your code will work. In addition, {return} needs to be part of a function. — Timbus Calin, Oct 18 '19 at 07:51
code works, but does not return `True`.. do i need to insert `print("true")? — sharks Tale, Oct 18 '19 at 07:54
@quamrana because if my list had more `"A"` it would print me multiple `"true"` values, whereas i just need just the 1 True — sharks Tale, Oct 18 '19 at 07:58
add a `break` after printing true once. So, `for x in list: if any(x == "A" in x): print True break` — Trollsors, Oct 18 '19 at 08:00
@Trollsors i like that idea. but does depend on what you're trying to achieve.. thanks — sharks Tale, Oct 18 '19 at 08:02
btw don't use `list` as a variable name. Try `lst` or `lis` ... — quamrana, Oct 18 '19 at 08:03
`list` is the name of the list type and if you use it as a variable name you cannot then convert something to a list using `list(something)`. — quamrana, Oct 18 '19 at 08:05

Aaron_ab · Accepted Answer · 2019-10-18T08:00:36.923

4

Can use Counter:

from collections import Counter

# hold in a 'dictionary' style something like: {'A':2, 'B':1, 'C':2}
c = Counter(['A','A','B', 'C', 'C'])

# check if 'A' appears more than 1 time. In case there is no 'A' in 
# original list, put '0' as default. 
c.get('A', 0) > 1 # 

>> True

edited Oct 18 '19 at 08:00

answered Oct 18 '19 at 07:58

Aaron_ab

3,450
3
28
42

Can that be changed to variable `list`? instead of using list inside the counter – sharks Tale Oct 18 '19 at 08:00

score 1 · Answer 2 · answered Oct 18 '19 at 07:55

return is used to return a value from function outside function block it wont work.

For a given list [1,2,3,4,1,1,3] .count(element) will return number of occurrences if it is greater than 1 you cam be sure that is has duplicates

You can try like this

for x in list:
    if "A" in x:
        print("true")
        print(list.count("A")) #count will return more that 1 if there are duplicates

score 1 · Answer 3 · answered Oct 18 '19 at 08:01

1

This code should do the trick:

def duplicate(mylist):
    for item in mylist:
        if mylist.count(item) > 1:
            return True
    return False

answered Oct 18 '19 at 08:01

Legorooj

2,646
2
15
35

score 1 · Answer 4 · answered Oct 18 '19 at 08:04

Return only works inside of a function.

Try this:

See here

def test(_list):
        d = {x:_list.count(x) for x in _list}
        result = [x for x in d.values()]
        if any(i > 1 for i in d.values()): 
            return True
        else: return False

_list = ["A", "A", "B", "A", "C"]  
print( test(_list) )

How to return True and false if duplicate value exists

4 Answers4