Data Types - Classifying Discoveries

Welcome back to camp, @name! Darwin here with another lesson from our expedition.

Every good researcher must know how to classify their discoveries. In Python, data also has different "species" - we call them data types.

Basic Data Types in Python

In the jungle we encounter different forms of life - animals, plants, insects. Similarly in Python we have different data types:

1. int (Integer) - Whole Numbers

1# Whole numbers - like the number of discovered species
2species_count = 42
3expedition_day = 7
4team_members = 5
5
6# Can be negative
7temperature_drop = -5
8depth_below_sea = -100
9
10# Python 3 supports very large numbers!
11huge_number = 999999999999999999999

2. float (Float) - Floating-Point Numbers

1# Numbers with a decimal part
2temperature = 32.5
3humidity = 78.3
4distance_km = 15.7
5
6# Scientific notation
7speed_of_light = 3e8  # 3 * 10^8 = 300000000
8tiny_number = 1.5e-10  # 0.00000000015

3. str (String) - Text

1# Text in single or double quotes
2explorer_name = "Darwin"
3location = 'Amazonia'
4
5# Multi-line strings (triple quotes)
6description = """
7This is a longer description
8spanning multiple lines
9of text.
10"""
11
12# Escape characters
13message = "Darwin said: \"Let's explore!\""
14path = "C:\\Users\\Darwin\\jungle"  # Windows path
15
16# Raw string (ignores escapes)
17path_raw = r"C:\Users\Darwin\jungle"

4. bool (Boolean) - Logical Values

1# Only two values: True or False
2is_dangerous = True
3found_water = False
4is_raining = True
5
6# The result of a comparison is a bool
7temperature = 35
8is_hot = temperature > 30  # True
9
10age = 15
11is_adult = age >= 18  # False

Checking Data Types - type()

1# The type() function shows the variable's type
2species_count = 42
3print(type(species_count))  # <class 'int'>
4
5temperature = 32.5
6print(type(temperature))  # <class 'float'>
7
8name = "Darwin"
9print(type(name))  # <class 'str'>
10
11is_safe = True
12print(type(is_safe))  # <class 'bool'>
13
14# Practical use
15data = 42
16if type(data) == int:
17    print("This is a whole number!")

Converting Between Types (Type Casting)

Sometimes we need to change the data type - like translating between languages:

String → Int/Float

1# String → Int
2age_text = "25"
3age = int(age_text)
4print(age + 5)  # 30
5
6# String → Float
7temperature_text = "32.5"
8temperature = float(temperature_text)
9print(temperature + 2.5)  # 35.0
10
11# WARNING! Error if the string is not a number
12# bad_conversion = int("abc")  # ValueError!

Int/Float → String

1# Int → String
2species_count = 42
3count_text = str(species_count)
4print("Discovered " + count_text + " species")  # String concatenation
5
6# Float → String
7temperature = 32.5
8temp_text = str(temperature)
9message = f"Temperature: {temp_text}°C"

Int ↔ Float

1# Int → Float
2whole_number = 10
3decimal_number = float(whole_number)  # 10.0
4
5# Float → Int (truncates the decimal part!)
6decimal = 15.7
7whole = int(decimal)  # 15 (NOT 16!)
8
9decimal2 = 15.2
10whole2 = int(decimal2)  # 15

Bool Conversions

1# Numbers → Bool
2# 0 = False, all others = True
3print(bool(0))    # False
4print(bool(1))    # True
5print(bool(-5))   # True
6print(bool(100))  # True
7
8# String → Bool
9# Empty string = False, non-empty = True
10print(bool(""))       # False
11print(bool("Darwin")) # True
12print(bool(" "))      # True (a space is a character!)
13
14# Bool → Int
15print(int(True))   # 1
16print(int(False))  # 0

Type-Specific Operations

Operations on Numbers (int, float)

1# Basic operations
2a = 10
3b = 3
4
5print(a + b)   # 13 (addition)
6print(a - b)   # 7  (subtraction)
7print(a * b)   # 30 (multiplication)
8print(a / b)   # 3.333... (division - ALWAYS float!)
9print(a // b)  # 3 (floor division)
10print(a % b)   # 1 (remainder - modulo)
11print(a ** b)  # 1000 (exponentiation: 10^3)
12
13# Operations on floats
14x = 5.5
15y = 2.5
16print(x + y)   # 8.0
17print(x * y)   # 13.75
18
19# Mixing int and float → result is float
20mixed = 10 + 5.5  # 15.5 (float)

Operations on Strings

1# Concatenation (joining)
2first_name = "Charles"
3last_name = "Darwin"
4full_name = first_name + " " + last_name
5print(full_name)  # Charles Darwin
6
7# Repetition
8jungle_cry = "Help! " * 3
9print(jungle_cry)  # Help! Help! Help!
10
11# String length
12name = "Darwin"
13print(len(name))  # 6
14
15# Indexing (from 0!)
16text = "Python"
17print(text[0])   # P
18print(text[1])   # y
19print(text[-1])  # n (last character)
20
21# Slicing
22word = "Expedition"
23print(word[0:4])   # Expe
24print(word[4:])    # dition
25print(word[:4])    # Expe
26print(word[::2])   # Eeiio (every other character)

None - Special Type

`None` is a special value meaning "no value":

1# None - like an empty box
2treasure = None
3print(treasure)  # None
4print(type(treasure))  # <class 'NoneType'>
5
6# Practical use
7def find_species(name):
8    if name == "Python regius":
9        return "Found!"
10    return None  # Not found
11
12result = find_species("Unknown")
13if result is None:
14    print("Unknown species")

Practical Example - Expedition Calculator

1print("=== Expedition Calculator ===\n")
2
3# Collecting data
4distance_text = input("Distance (km): ")
5time_text = input("Time (hours): ")
6team_size_text = input("Team size: ")
7
8# Converting to appropriate types
9distance = float(distance_text)
10time = float(time_text)
11team_size = int(team_size_text)
12
13# Calculations
14avg_speed = distance / time
15distance_per_person = distance / team_size
16
17# Displaying results
18print("\n--- RESULTS ---")
19print(f"Average speed: {avg_speed:.2f} km/h")
20print(f"Distance per person: {distance_per_person:.2f} km")
21print(f"Type of distance: {type(distance)}")
22print(f"Type of team_size: {type(team_size)}")

Practical Exercise

Create a program that:

1. Asks for a temperature in Fahrenheit
2. Converts it to Celsius: C = (F - 32) × 5/9
3. Displays the result
4. Tells you whether it's hot (>30°C), normal (15-30°C), or cold (<15°C)

Summary

In this lesson you learned:

• ✅ Basic data types: int, float, str, bool, None
• ✅ Checking types with `type()`
• ✅ Converting between types (type casting)
• ✅ Type-specific operations

Checkpoint

Before moving on:

• [ ] You understand the difference between int and float
• [ ] You can convert types
• [ ] You know the difference between `/` and `//`
• [ ] You understand string indexing

In the next lesson Darwin will show you operators - the explorer's mathematical and logical tools! 🔧🌴