Check if the integer in a list is not duplicated, and sequential

Question

testGroupList is a list of integer. I need to check the numbers in testGroupList is sequential and not duplicate numbers. Ignore the negative integer.

For example, [1,2,-1,2,3,4] is an error as 2 is duplicated, but [-1,3,2,4,1,5] is OK.

I implemented it as follows, and it's pretty ugly. Is there any clever way to do this?

    buff = filter(lambda x: x > 0, testGroupList) 
    maxval = max(buff) 
    for i in range(maxval): 
        id = i+1 
        val = buff.count(id) 
        if val == 1: print id, 
        elif val >= 2: print "(Test Group %d duplicated %d times)" % (id, val), 
        elif val == 0: print "(Test Group %d missing)" % id,

Answer 1

For Python2.7 or 3.1 you can use Counter, although the print needs to be changed in the case of Python3

from collections import Counter
counter = Counter(x for x in testGroupList if x>=0)
minval = min(Counter) 
maxval = max(Counter)
messages={0:"(Test Group %(id)d missing)",
          1:"%(id)d",
          2:"(Test Group %(id)d duplicated %(val)d times)"}
for id in range(minval,maxval+1): 
    val = counter[id]
    print(messages[min(val,2)]%vars())

For older Python use defaultdict

from collections import defaultdict
counter = defaultdict(int)
for k in testGroupList:
    if k>=0:counter[k]+=1

minval = min(counter) 
maxval = max(counter)
messages={0:"(Test Group %(id)d missing)",
          1:"%(id)d",
          2:"(Test Group %(id)d duplicated %(val)d times)"}
for id in range(minval,maxval+1): 
    val = counter[id]
    print messages[min(val,2)]%vars(),

Answer 2

for i, v in enumerate(buff):
    if i != v - 1:
        print "MISSING OR DUPLICATE"

Answer 3

If you don't need fancy error reporting, then you can implement it as two simple checks:

positiveValues = [x for x in testGroupList if x > 0]
if len(positiveValues) != len(set(positiveValues)):
    print("Input has duplicate values")
elif len(positiveValues) != max(positiveValues):
    print("Input has missing values")

Answer 4

If you're looking for more elegant as in smaller code, then you can just do this:

buff = [x for x in testGroupList if x > 0]
for i, val in enumerate([buff.count(x) for x in xrange(1,max(buff))]):
    if val == 1: print i+1, 
    elif val > 1: print "(Test Group %d duplicated %d times)" % (i+1, val), 
    elif val == 0: print "(Test Group %d missing)" % (i+1),

which is pretty close to your original. I used i instead of id because id is a standard function in Python.