Latest Questions 209 total
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181What is Node.js and why is it used?
Node.js is a JavaScript runtime built on Chrome's V8 engine that lets you run JavaScript on the server side.
**Why use it:**
- **Non-blocki...
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182What is the difference between SQL and NoSQL databases?
**SQL (Relational):** MySQL, PostgreSQL, SQLite
- Structured tables with fixed schema
- ACID compliant (reliable transactions)
- Best for co...
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183What is REST API and how does it work?
REST (Representational State Transfer) is an architectural style for building APIs.
Key principles:
- **Stateless** — each request is ind...
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184What is the difference between React and Angular?
| Feature | React | Angular |
|---|---|---|
| Type | Library | Full framework |
| Language | JavaScript | TypeScript |
| Learning curve | Mo...
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185What is the difference between correlation and causation?
**Correlation** — two variables change together (positive or negative relationship)
**Causation** — one variable directly causes the cha...
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186What is Pandas and how is it used in data science?
Pandas is a Python library for data manipulation and analysis. It provides two main data structures:
**Series** — 1D labelled array
**Dat...
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187What is feature engineering in machine learning?
Feature engineering is the process of using domain knowledge to create, transform, or select input variables (features) that help ML models ...
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188What is the difference between mean, median, and mode?
**Mean** — sum divided by count. Sensitive to outliers.
**Median** — middle value when sorted. Robust to outliers.
**Mode** — most fre...
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189What is the data science lifecycle?
The data science lifecycle has 6 stages:
1. **Business Understanding** — define the problem
2. **Data Collection** — gather relevant da...
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190What is overfitting and how do you prevent it?
Overfitting occurs when a model learns the training data too well (including noise), so it performs poorly on new data.
**Signs:** High tra...
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191How does a transformer model work?
A Transformer uses **self-attention** to process all tokens in a sequence simultaneously (unlike RNNs which process sequentially).
Key comp...
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192What is the difference between supervised and unsupervised learning?
**Supervised learning** — model learns from labelled data (input → output pairs)
- Examples: Linear regression, Random Forest, SVM
- Use...
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193What is LangChain and why is it used?
LangChain is a framework for building applications with Large Language Models (LLMs).
It provides:
- **Chains** — link multiple LLM calls...
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194What is the difference between == and is in Python?
**==** checks value equality — are the values the same?
**is** checks identity — are they the exact same object in memory?
```python
a ...
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195Explain list comprehension in Python with examples
List comprehension is a concise way to create lists.
```python
# Traditional way
squares = []
for x in range(10):
squares.append(x**2)
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