Hello Guys,
im new to Pytorch and DL in genereal, so i hope this is the right place to ask questions like this 
I wanted to create my first record, but my record becomes infinite. This problem should be easiest to show with the codes and outputs.
class DataframeDataset(Dataset):
    """Load Pytorch Dataset from Dataframe
    
    """

    def __init__(self, data_frame, input_key, target_key, transform=None, features=None):
        self.data_frame = data_frame
        self.input_key = input_key
        self.target_key = target_key
        self.inputs = self.data_frame[input_key]
        self.targets = self.data_frame[target_key]
        self.transform = transform
        self.features = [input_key, target_key] if features is None else features
        self.len = len(self.inputs)

    def __len__(self):
        return self.len

    def __str__(self):
        return str(self.info())

    def info(self):
        info = {
            'features': self.features,
            'num_rows': len(self)
        }
        return info

    def __getitem__(self, idx):
        if torch.is_tensor(idx):
            idx = idx.tolist()

        data = {
            self.input_key: self.inputs[idx],
            self.target_key: self.targets[idx]
        }

        if self.transform:
            return self.transform(data)

        return data

lets look at some mook data:
    data = [("x1", "y2", "A3"), ("x1", "y2", "b3"), ("x1", "y2", "c3"), ("x1", "y2", "d3")]
    df = pd.DataFrame(data, columns=['input', 'target', 'random'])
    print(df.head())

  input target random
0    x1     y2     A3
1    x1     y2     b3
2    x1     y2     c3
3    x1     y2     d3

    ds = DataframeDataset(data_frame=df, input_key="input", target_key="target", transform=None)
    print("*" * 40)
    print("Len:", len(ds))
    print("Ds", ds)
    print(ds[0])

Len: 4
Ds {'features': ['input', 'target'], 'num_rows': 4}
{'input': 'x1', 'target': 'y2'}

So the basic functions seem to work. However, if I want to iterate over the data with a foreach loop, then unfortunately the loop does not know the boundaries. So I get a key-error, because the torch accesses indicies outside the boundary.
    for idx, data in enumerate(ds):
        print(idx,"->",data)

0 -> {'input': 'x1', 'target': 'y2'}
1 -> {'input': 'x1', 'target': 'y2'}
2 -> {'input': 'x1', 'target': 'y2'}
3 -> {'input': 'x1', 'target': 'y2'}
Traceback (most recent call last):
  File "/home/warmachine/.local/lib/python3.8/site-packages/pandas/core/indexes/range.py", line 351, in get_loc
    return self._range.index(new_key)
ValueError: 4 is not in range

By changing the __len__ function, somehow nothing changes. If I let the function always return 0, for example, I get the same error.
    def __len__(self):
        return 0

 → 
    ds = DataframeDataset(data_frame=df, input_key="input", target_key="target", transform=None)
    print("*" * 40)
    print("Len:", len(ds))
    print("Ds", ds)

    for idx, data in enumerate(ds):
        print(idx,"->",data)

Len: 0
Ds {'features': ['input', 'target'], 'num_rows': 0}
{'input': 'x1', 'target': 'y2'}
0 -> {'input': 'x1', 'target': 'y2'}
1 -> {'input': 'x1', 'target': 'y2'}
2 -> {'input': 'x1', 'target': 'y2'}
3 -> {'input': 'x1', 'target': 'y2'}
Traceback (most recent call last):
  File "/home/warmachine/.local/lib/python3.8/site-packages/pandas/core/indexes/range.py", line 351, in get_loc
    return self._range.index(new_key)
ValueError: 4 is not in range

What am i doing wrong?

if i leave __len__ at self.len and i try this:
    for idx in range(0, len(ds)):
        data = ds[idx]
        print(idx,"->",data)

Everything works as expected, so what am i doing wrong?
1 -> {'input': 'x1', 'target': 'y2'}
2 -> {'input': 'x1', 'target': 'y2'}
3 -> {'input': 'x1', 'target': 'y2'}

Process finished with exit code 0

I would pref to use it without range.
Ty in advanced