CODEWITHSUNDEEP
pythonlist
Schegge
Schegge

Reputation: 13

Checking numbers inbetween integers in a list

I have a list in which 50 random numbers, ranging from 1 up to 1000, are sorted smallest to biggest. I want to find any number in between these numbers yet not including them. The problem is that when numbers follow each other directly (100, 101, 102) they are still getting printed even though the should not. (the code is written in Python 3.2.3)

I tried to take the first integer of the list an compare it to the second integer adding + 1 to the first one until it would eventually become as big as the second one. Then I would compare the second to the third one etc.

list = [98, 100, 101, 102, 103, 110, ... ]
position_counter_1 = 0
position_counter_2 = 1
position_1 = 0
position_2 = 1

    while position_counter_2 < len(list):

        if list[position_1] + 1 != list[position_2] :

            while list[position_counter_1] <= list[position_counter_2] - 1 :
                list[position_counter_1] = list[position_counter_1] + 1
                print(list[position_counter_1])

                if list[position_counter_1] >= list[position_counter_2] - 1 :
                 position_counter_1 = position_counter_1 + 1
                 position_counter_2 = position_counter_2 + 1

The output is 99 101 102 103 104 105 106 107 108 109, it should be 99 104 105 106 107 108 109.

Also I get the following error massage, which is not that bad since it only appears when the loop is done yet here it is:

while list[position_counter_1] <= list[position_counter_2] - 1 :

IndexError: list index out of range

Upvotes: 1

Views: 115

Answers (5)

Dschoni
Dschoni

Reputation: 3862

I'm suggesting an easier approach without nested loops:

my_list = [98, 100, 101, 102, 103, 110, ... ]
for i in range(1000):
    if i not in my_list:
        print(i)

Upvotes: 0

ncica
ncica

Reputation: 7206

list = [98, 100, 101, 102, 103, 110 ]

for i in range (list[0], list[-1]):
    if i not in list:
        print (i)

output:

99
104
105
106
107
108
109

or list comprehension

print ([i for i in range (list[0], list[-1]) if i not in list])

Upvotes: 0

bart
bart

Reputation: 1048

You can use the range(start, stop, step) function:

start - position to start. Default is 0

stop - position to end, not included.

step - the incrementation. Default is 1

list = [98, 100, 101, 102, 103, 110]

for i in range(1,1001):
    if i not in list:
        print(i)

the output is:

... 99 104 105 106 107 108 109 ...

Upvotes: 0

ipaleka
ipaleka

Reputation: 3957

It's Python, don't complicate things. :)

mylist = [98, 100, 101, 102, 103, 110]
[num for num in range(mylist[0]+1, mylist[-1]) if num not in mylist]

Python 3 range creates an iterator of all the integer numbers between the first argument (and includes it) and the second argument (not including it). So this list comprehension task from above creates a new list of all the numbers (mylist[0] returns the first and mylist[-1] returns the last integer), but doesn't include those already presented in the list (if num not in mylist condition.)

Upvotes: 2

palvarez
palvarez

Reputation: 1598

You can use sets :)

list1 = [98, 100, 101, 102, 103, 110]
full = set(range(list1[0], list1[-1] + 1))
result = full - set(list1)
print(result)
# {99, 104, 105, 106, 107, 108, 109}

Here I'm creating a list with range of all numbers between the range of your list, always assumming it is ordered, otherwise you can use sorted(). Then casting it to set and just doing some difference of sets.

Upvotes: 0

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