CODEWITHSUNDEEP
pythonlist
kc9552
kc9552

Reputation: 25

How to read from a file and add non duplicate numbers to a list in Python?

I am reading a file that has hundreds of numbers (which are repeated) from 1 to 1000. I wanted to create a list of all the unique numbers in the file. The way I am doing it (see the attached code), any number after 9, i.e. 10 and above are being ignored and therefore not stored in the list.

TID = 0
items = []
f = open(dataset_name, 'r', encoding="utf8")
for row in f:
    TID = TID + 1
    for item in row:
        if item not in items:
            items.append(item)

Upvotes: 0

Views: 49

Answers (3)

cco
cco

Reputation: 6291

As others have said, the for item in row: loop is causing your code to look at individual characyers, not each line as a number.
For data this small, a simple solution is to read all of the data at once, i.e.

With open('jutska.txt', 'r', encoding="utf8") as f:
    itemlist = f.read().split()
    TID = len(itemlist)
    items = set(int(item) for item in itemlist)

If you didn't need the count of lines (TID), you could use

With open('jutska.txt', 'r', encoding="utf8") as f:
    items = set(int(item) for item in f.read().split())

Upvotes: 1

mattiast
mattiast

Reputation: 1944

I believe you have one iterator too many: row is a line in the file, and

for item in row:

will iterate over the characters in the line.

Also Python has set data structure for this purpose, I believe you can do this:

TID = 0
items = set()
f = open('jutska.txt', 'r', encoding="utf8")
for row in f:
    TID = TID + 1
    items.add(row.strip())

Note the use of strip to get rid of the newline at the end, and conversion to int.

Upvotes: 0

EdvardM
EdvardM

Reputation: 3082

Aren't you iterating over each digit in any number, which are still strings when you read them? So relevant part should be

seen = []
...
for line in f:
    if line not in seen:
        seen.append(line)

There are better data structures you can use for checking if an item has been seen though, but in this case it shouldn't matter.

Upvotes: 1

Related Questions