Python：从.txt文件填充对象列表

Question

For starters I've programmed in C++ for the past year and a half, and this is the first time I'm using Python.

The objects have two int attributes, say i_ and j_.

The text file is as follows:

1,0
2,0
3,1
4,0
...

What I want to do is have the list filled with objects with correct attributes. For example,

print(myList[2].i_, myList[2].j_, end = ' ')

would return

3 1

Here's my attempt after reading a little online.

class myClass:
    def __init__(self, i, j):
        self.i_ = i
        self.j_ = j   

with open("myFile.txt") as f:

    myList = [list(map(int, line.strip().split(','))) for line in f]

    for line in f:
        i = 0
        while (i < 28):
            myList.append(myClass(line.split(","), line.split(",")))
            i +=1

But it doesn't work obviously.

Thanks in advance!

Answer 1

Since you're working with a CSV file you might want to use the csv module. First you would pass the file object to the csv.reader function and it will return an iterable of rows from the file. From there you can cast it to a list and slice it to the 29 rows you are required to have. Finally, you can iterate over the rows (eg [1,0]) and simply unpack them in the class constructor.

class MyClass:
    def __init__(self, i, j):
        self.i = int(i)
        self.j = int(j)

    def __repr__(self):
        return f"MyClass(i={self.i}, j={self.j})"

with open('test.txt') as f:
    rows = [r.strip().split(',') for r in f.readlines()[:29]]
    my_list = [MyClass(*row) for row in rows]

for obj in my_list:
    print(obj.i, obj.j)

print(len(my_list))

Answer 2

I'm not sure what you're trying to do with myList = [list(map(int, line.strip().split(','))) for line in f] . This will give you a list of lists with those pairs converted to ints. But you really want objects from those numbers. So let's do that directly as we iterate through the lines in the file and do away with the next while loop:

my_list = []
with open("myFile.txt") as f:
    for line in f:
        nums = [int(i) for i in line.strip().split(',') if i]
        if len(nums) >= 2:
            my_list.append(myClass(nums[0], nums[1]))

Answer 3

I not sure you really what to stick with this format

print(myList[2].i_, myList[2].j_, end = ' ')

My solution is quite manual coded and i am using dictionary to store i and j

result = {'i':[],
  'j':[]}

and below is my code

result = {'i':[],
      'j':[]}

with open('a.txt', 'r') as myfile:
    data=myfile.read().replace('\n', ',')
print(data)

a = data.split(",")
print (a)

b = [x for x in a if x]
print(b)

for i in range( 0, len(b)):
    if i % 2 == 0:
        result['i'].append(b[i])
    else:
        result['j'].append(b[i])


print(result['i'])
print(result['j'])
print(str(result['i'][2])+","+ str(result['j'][2]))

The result: 3,1