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The problem is that you are using row twice with different types. for row in self.diagram: # row is str here for row in self.seed_diagram: # row is list[str] here Renaming one or the other m...
Answer
#2: Post edited
by
Moshi
·
2022-12-28T01:38:08Z (almost 2 years ago)
Python's initialization-is-declaration philosophy makes this wording a bit confusing
The problem is that you are declaring `row` twice.- ```py
- for row in self.diagram: # row is str here
- ```
- ```py
- for row in self.seed_diagram: # row is list[str] here
- ```
- Renaming one or the other makes the error go away.
Why does this happen? Python has some somewhat counterintuitive odd scoping rules. Take the following example:- ```py
- def foo():
- l = [["hello"], ["world"]]
- for x in l:
- for y in x:
- pass
- print(y)
- foo()
- ```
- The `foo` call actually prints `world`! In Python, loops (and other conditionals) do not create a new block scope, and so in fact both `row` variables in your code are one and the same, scoped to the function, and so mypy gets upset when you try to use it with different types.
- The problem is that you are using `row` twice with different types.
- ```py
- for row in self.diagram: # row is str here
- ```
- ```py
- for row in self.seed_diagram: # row is list[str] here
- ```
- Renaming one or the other makes the error go away.
- Why does this happen? Python has some somewhat counterintuitive scoping rules. Take the following example:
- ```py
- def foo():
- l = [["hello"], ["world"]]
- for x in l:
- for y in x:
- pass
- print(y)
- foo()
- ```
- The `foo` call actually prints `world`! In Python, loops (and other conditionals) do not create a new block scope, and so in fact both `row` variables in your code are one and the same, scoped to the function, and so mypy gets upset when you try to use it with different types.
#1: Initial revision
by
Moshi
·
2022-12-28T01:34:51Z (almost 2 years ago)
The problem is that you are declaring `row` twice.
```py
for row in self.diagram: # row is str here
```
```py
for row in self.seed_diagram: # row is list[str] here
```
Renaming one or the other makes the error go away.
Why does this happen? Python has some somewhat counterintuitive odd scoping rules. Take the following example:
```py
def foo():
l = [["hello"], ["world"]]
for x in l:
for y in x:
pass
print(y)
foo()
```
The `foo` call actually prints `world`! In Python, loops (and other conditionals) do not create a new block scope, and so in fact both `row` variables in your code are one and the same, scoped to the function, and so mypy gets upset when you try to use it with different types.