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I ran 20 lines of Python through an AI code analyzer. It found 6 issues I missed — including a critical one.

#python #webdev #security #beginners

I thought my Python code was fine. It ran without errors, did what I needed, and I had reviewed it manually three times.
Then I pasted it into an AI code analyzer. It came back with a Health Score of 60/100 and 6 issues.Here's the exact code I analyzed (20 lines, looks innocent):


What the analyzer found

CRITICAL — SQL Injection (Line 7)

The code:

query = "SELECT * FROM users WHERE name = '" + name + "'"
cursor.execute(query)
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This is the worst kind of bug — the code runs perfectly, but an attacker can type ' OR '1'='1
and get your entire database. No error, no warning, just silent data exposure.

The fix:

cursor.execute(
    "SELECT * FROM users WHERE name = ?",
    (name,)
)
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HIGH — Mutable Default Argument (Line 12)

The code:

def process_data(items=[]):
    items.append("new_item")
    return items
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Classic Python trap. The list [] is created once when the function is defined, not every time it's
called. Every call shares the same list and keeps growing. This causes bugs that are almost impossible to track down.
The fix:

def process_data(items=None):
    if items is None:
        items = []
    items.append("new_item")
    return items
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MEDIUM — Hardcoded API Key (Line 1)

The code:

API_KEY = "sk-abc123xyz789secretkey"
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One accidental GitHub push and your API key is public forever. Bots scan GitHub 24/7 for exactly
this pattern.

The fix:

import os
API_KEY = os.environ.get("API_KEY")
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LOW x3 — Missing Type Hints (Lines 14, 17, 19)

Not dangerous, but makes your code harder to read and maintain. Type hints also help IDEs catch bugs before runtime.
The tool I used LearnCodeGuide (https://learncodeguide.com) — paste your code, pick Security/Debug/Refactor mode, get
exact line references with explanations and fixes in under 5 seconds. Free 7-day trial, no credit card needed.
What I learned
The SQL injection was in code I had reviewed manually three times and missed every time. The mutable default argument was something I didn't even know was a Python issue until the analyzer flagged it.
AI doesn't replace understanding your code — but it catches the things your eyes skip over.
What's the worst bug you've found in your own code after the fact? Drop it in the comments.

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