How do you check if a list has repeated variable in python?

Question

I'm trying to generate a random list of 7 values and want to check the list for duplicate numbers and remove those from the list. I currently have:

import random
acard1 = random.randrange(0,13,1)
acard2 = random.randrange(0,13,1)
acard3 = random.randrange(0,13,1)
acard4 = random.randrange(0,13,1)
acard5 = random.randrange(0,13,1)
acard6 = random.randrange(0,13,1)
acard7 = random.randrange(0,13,1)
myhand=[acard1, acard2, acard3, acard4, acard5, acard6, acard7]
print(myhand)

How would I check if there are repeated values and then remove those values?

For example, if my list were [11, 7, 11, 12, 9, 9, 10], how would I have my program recognize that 11 and 9 are repeated and turn the list into [7, 12, 10]?

`set` won't work. there will still be one copy of the number. — kindall, Jul 14 '17 at 22:25
`[value for value, count in Counter(values).items() if count == 1]`, maybe? It won't necessarily keep input order, though. — jonrsharpe, Jul 14 '17 at 22:30
count the presence of each number and discard it if there is more than one. — wwii, Jul 14 '17 at 22:39

score 2 · Answer 1 · answered Jul 14 '17 at 22:28

2

Here's a simple technique using collections.Counter:

In [451]: from collections import Counter

In [453]: c = Counter(l)

In [454]: [x for x in l if c[x] == 1]
Out[454]: [7, 12, 10]

Any answers with a list comprehension using l.count(x) are definitely going to be slower than this.

answered Jul 14 '17 at 22:28

cs95

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```[k for k, v in c.items() if v == 1]``` – wwii Jul 14 '17 at 22:41
@wwii That doesn't guarantee the same order, `Counter` objects do not maintain order I believe. – cs95 Jul 14 '17 at 22:42
Ahh, well I didn't see the spec for maintaining order. – wwii Jul 14 '17 at 22:43
1

@cᴏʟᴅsᴘᴇᴇᴅ [Yup](https://docs.python.org/3.6/library/collections.html#collections.Counter): _"It is an unordered collection [...]"_ – Christian Dean Jul 14 '17 at 22:44

score 0 · Answer 2 · answered Jul 14 '17 at 22:29

Maybe create a list where you keep unique entries by checking if index number is taken? Make index 1 contain the number 1, index 2 contains number 2, and so on.

Alternatively you could search through the entire list to check if 11 is already present somewhere. Depending on language and type of list, you could delete the element at the specific index, og simply append to a new "unique" list as i attempted to describe above.

How do you check if a list has repeated variable in python?

2 Answers2