Variables and data types

Variables and Data Types

Variables are how your program stores information. Understanding them is the foundation for everything in AI.

What is a Variable?

In Python you don't need to declare the type — it's inferred automatically.

name = "Ahmed"        # text (str)
age = 25              # integer (int)
score = 98.5          # decimal (float)
is_student = True     # boolean (bool)

Basic Data Types

| Type | Name | Example | Use in AI | |------|------|---------|----------| | int | Integer | 42 | epoch count, batch size | | float | Decimal | 0.001 | learning rate, accuracy | | str | Text | "GPT" | model names, text data | | bool | Boolean | True | flags, training conditions |

List

scores = [95, 87, 92, 88, 91]
models = ["GPT-4", "Claude", "Gemini"]
print(scores[0])    # 95
print(models[-1])   # Gemini
print(scores[1:3])  # [87, 92]
models.append("Llama")

Dictionary

model_info = {
    "name": "Claude",
    "company": "Anthropic",
    "context": 200000,
}
print(model_info["name"])    # Claude
model_info["version"] = "claude-opus-4-5"

Tuple and Set

dimensions = (224, 224, 3)       # CNN image size — immutable
unique_labels = {0, 1, 2, 1, 0}
print(unique_labels)  # {0, 1, 2}

f-Strings

model = "Claude"
accuracy = 94.7
result = f"Model {model} reached {accuracy}%"
print(result)

Lesson Summary

• Variables: a name pointing to a value in memory
• Basic types: int · float · str · bool
• Lists: ordered and mutable
• Dictionaries: key-value, fast lookup
• f-strings: best way to build strings in modern Python