Numbers, Strings & Operators¶

# Arithmetic operators
print(7 + 2)     # 9   — add
print(7 - 2)     # 5   — subtract
print(7 * 2)     # 14  — multiply
print(7 / 2)     # 3.5 — true division ALWAYS returns float
print(7 // 2)    # 3   — floor division: rounds toward negative infinity
print(7 % 2)     # 1   — modulo (remainder)
print(7 ** 2)    # 49  — exponentiation
print(-7 // 2)   # -4  — floor division: rounds DOWN, not toward zero!

# Arbitrary precision in action:
print(2 ** 100)  # 1267650600228229401496703205376 — no overflow

# Integer bit operations (useful for flags and binary data):
print(0b1010 & 0b1100)  # 8  — bitwise AND
print(0b1010 | 0b1100)  # 14 — bitwise OR
print(1 << 4)            # 16 — left shift (multiply by 2^4)

# The classic float trap:
print(0.1 + 0.2)           # 0.30000000000000004
print(0.1 + 0.2 == 0.3)    # False!

# Workaround 1: math.isclose() for approximate comparisons
import math
print(math.isclose(0.1 + 0.2, 0.3))    # True — within relative tolerance

# Workaround 2: Decimal for exact arithmetic (use for money)
from decimal import Decimal, ROUND_HALF_UP

price    = Decimal("19.99")    # always pass a STRING to Decimal
tax_rate = Decimal("0.08")
tax      = price * tax_rate
total    = price + tax
total_rounded = total.quantize(Decimal("0.01"), rounding=ROUND_HALF_UP)

print(f"Tax:   ${tax}")          # 1.5992 — exact
print(f"Total: ${total_rounded}") # 21.59

# Workaround 3: store integer cents
price_cents = 1999    # $19.99 stored as cents
tax_cents   = price_cents * 8 // 100  # integer division
print(f"Total: ${(price_cents + tax_cents) / 100:.2f}")   # $21.59

# String literals
s1 = "Hello, world"
s2 = 'same thing'
s3 = """multi
line
string"""
path = r"C:\Users\Ada\Documents"   # raw: backslashes are literal

# f-string format mini-language:
name, revenue, pct = "Acme", 1_234_567.89, 0.1234

print(f"{name:<12}")            # "Acme        " (left-align, width 12)
print(f"${revenue:,.2f}")       # "$1,234,567.89"
print(f"{pct:.1%}")             # "12.3%"
print(f"{name=}")               # "name='Acme'" — debug form (3.8+)
print(f"{2 ** 10:,}")           # "1,024" (any expression in braces)

s = "  Hello, Solutions World  "

# Cleaning:
print(s.strip())               # "Hello, Solutions World"
print(s.lower())               # "  hello, solutions world  "
print(s.upper())               # "  HELLO, SOLUTIONS WORLD  "

# Searching and replacing:
print(s.strip().startswith("Hello"))   # True
print("Solutions" in s)          # True (membership test)
print(s.replace("World", "Team"))  # new string — immutable!

# Splitting and joining:
words = "Acme,Globex,Initech".split(",")   # ["Acme", "Globex", "Initech"]
print(" | ".join(words))               # "Acme | Globex | Initech"

# Slicing (same syntax as lists):
text = "solutions"
print(text[0:4])     # "solu"
print(text[-4:])     # "ions"
print(text[::-1])    # "snoitulos"  (reversed)

text  = "café"                       # str — Unicode text
bdata = text.encode("utf-8")      # str → bytes: b'caf\xc3\xa9'
back  = bdata.decode("utf-8")     # bytes → str: "café"

print(type(bdata))   # <class 'bytes'>
print(bdata)         # b'caf\xc3\xa9'
print(back)          # café

# File modes:
# open("f.txt", "r")  → yields str (text mode, decodes via locale)
# open("f.bin", "rb") → yields bytes (binary mode, no decoding)

# Rule: use UTF-8 everywhere unless you have a specific reason not to.
# Always specify encoding explicitly when opening text files:
with open("data.txt", "r", encoding="utf-8") as f:
    content = f.read()