Decisions I

Formatted Strings (f-strings)

• f-string: String prefixed with f that replaces expressions inside braces {} with their values.
• Simplifies mixing text and variables without concatenation.

name = "Alex"
print(f"Hello, {name}!")

Floating-Point Numbers

• float: Numbers with a fractional part; e.g. 3.14, 2.0.
• Division (/) of two ints produces a float.
• type(value) returns a variable's data type.
• Format floats in f-strings using e.g. {value:.2f}

x = 8
y = 3
z = x / y
print(z)                # 2.6666666666666665
print(type(z))          # <class 'float'>
print(f"{z:.2f}")       # 2.67

Rounding & Truncating Floats

• round(value, 2) returns a float rounded to two decimal places.
• int(value) returns an int after truncating the fractional part.

z = 2.6666666666666665
print(round(z, 2))      # 2.67
print(int(z))           # 2

Booleans

• Boolean (bool): Data type that can be only one of two values: True or False.
• Comparison operators ==, !=, <, <=, >, >= return bool values.

print(3 < 5)   # True
print(2 == 3)  # False

Floating-Point Surprises

• Some floats cannot be represented exactly in memory, leading to tiny tiny errors. Consequently, directly comparing floats with == may fail.
• Use math.isclose() for safer comparisons.

import math
total = 0.1 + 0.1 + 0.1
print(total == 0.3)              # False
print(math.isclose(total, 0.3))  # True

• The decimal module can provide exact decimal arithmetic, but this is rarely needed.

Conditional Logic

• if executes a block (or suite) of code when its condition is True.
• else handles the complementary case.
• The entire block of code following if or else must be indented by 4 spaces.

if condition:
    # code to execute if condition is True (nothing happens if False)

if condition:
    # code to execute if condition is True
else:
    # code to execute if condition is False