Python error: AttributeError: 'int' object has no attribute 'append'

Question

So I've looked through similar questions, and I'm still getting the same problem and can't figure it out. For this programming assignment, I'm creating a simplified version of lexical analysis for a small subset of the Clite lexicon. I'm extracting tokens from an input file, outputting the results of my analysis. I'm creating a symbol table for the identifiers founds using a dictionary. When I find the same identifiers on different lines, I need to append to the symbol table the line that it was found on. For example, I find the identifier "number18" on line 2 and again on line 7. So the symbol table would need to go from {number18: 2} to {number18: 2,7} The problem comes when I try to append the new line number onto a current dictionary entry. I get the error as I posted in the question title. Here's my code thus far ``` y = 0 s2 = () stable = dict() for line in open("Sample.txt","r"): x1 = '' for char in line: if char.isalpha(): x1 = x1 + char elif char.isdigit(): x1 = x1 + char eli…

Accepted Answer

You first set your `dict` values to be an `int`:

```
    stable[x1]=y
```

but then you later on you try to treat it as if it is a `list`:

```
    stable[x1].append(y)
```

Start out with a `list` containing your first `int` instead:

```
    stable[x1]=[y]
```

and the `.append()` will work.

Alternatively, you could use a `defaultdict`:

```
stable = defaultdict(list)
```

and then append at will without needing to test if the key is already there:

```
    stable[x1].append(y)  # No need to do `if x1 in stable`.
```

Python error: AttributeError: 'int' object has no attribute 'append'

Solution

Problem