python - Error from Pycharm: Expected type 'SupportsIndex | slice', got 'str' instead - Stack Ov

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My input file, infile is as follows:

NUMBER,SYMBOL
1,AAPL
2,MSFT
3,NVDA

Here is my code:

import csv

infile = "stock-symbols-nasdaq-SO.csv"

with open(infile, encoding='utf-8') as csvfile:
    reader = csv.DictReader(csvfile)  # Read CSV as a dictionary
    for row in reader:
        print(row)
        symbol = row['SYMBOL']  # Error from Pycharm: Expected type 'SupportsIndex | slice', got 'str' instead
        print(symbol)

This code "appears" to run correctly, but why is Pycharm indicating an error? Is their anything that I can do to remove it?

My input file, infile is as follows:

NUMBER,SYMBOL
1,AAPL
2,MSFT
3,NVDA

Here is my code:

import csv

infile = "stock-symbols-nasdaq-SO.csv"

with open(infile, encoding='utf-8') as csvfile:
    reader = csv.DictReader(csvfile)  # Read CSV as a dictionary
    for row in reader:
        print(row)
        symbol = row['SYMBOL']  # Error from Pycharm: Expected type 'SupportsIndex | slice', got 'str' instead
        print(symbol)

This code "appears" to run correctly, but why is Pycharm indicating an error? Is their anything that I can do to remove it?

• python
• pycharm
• python-typing

Share Improve this question Follow edited Mar 10 at 16:58 Daraan 4,24277 gold badges2222 silver badges4747 bronze badges asked Mar 10 at 16:44 Charles KnellCharles Knell 64344 silver badges1616 bronze badges 5

• 2 Looks a bit like a bug/wrong type-inference, row should be a dict, the error indicates that row is inferred as a list. – Daraan Commented Mar 10 at 16:56
• 2 What version of PyCharm? Looks like this bug which was supposedly fixed. But there are comments as recent as 6 months ago saying it's still happening. – Barmar Commented Mar 10 at 17:12
• When I run this code, I'm not getting any errors. @Barmar might be right, this might be a bug in an older version – ServerS Commented Mar 10 at 17:13
• 2 @ServerS It's not an error you get when running the code, just in PyCharm's type hints. – Barmar Commented Mar 10 at 17:13
• Comparing linter output from multiple tools, including pyright and mypy —strict, is always a fun game. – J_H Commented Mar 10 at 19:43

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1 Answer 1

Sorted by: Reset to default 0

A solution to this is to use a type hint for row as follows:

with open(infile, encoding='utf-8') as csvfile:
    reader = csv.DictReader(csvfile)  # Read CSV as a dictionary
    for row in reader:
        print(row)
        row: dict[str, str]  # type hint which specifies that row is a dict with string keys and values
        symbol = row['SYMBOL']
        print(symbol)

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