# Single quotes
name = 'Alice'

# Double quotes
greeting = "Hello, World!"

# Triple quotes (multi-line)
paragraph = """This is a
multi-line string that
preserves line breaks."""

# Raw strings (ignore escape characters)
path = r"C:\Users\name\documents"

# Byte strings
data = b"binary data"

 P  y  t  h  o  n
 0  1  2  3  4  5    (positive index)
-6 -5 -4 -3 -2 -1   (negative index)

text = "Python"

# Indexing
print(text[0])    # P
print(text[3])    # h
print(text[-1])   # n
print(text[-3])   # h

# Slicing: [start:stop:step]
print(text[0:3])    # Pyt (characters 0, 1, 2)
print(text[2:5])    # tho
print(text[:3])     # Pyt (from beginning)
print(text[3:])     # hon (to end)
print(text[::2])    # Pto (every 2nd character)
print(text[::-1])   # nohtyP (reversed)

# Slicing with negative indices
print(text[-3:])    # hon
print(text[:-3])    # Pyt
print(text[-4:-1])  # tho

text = "Hello"

# This will raise TypeError
# text[0] = "h"  # TypeError: 'str' object does not support item assignment

# Instead, create a new string
text = "h" + text[1:]
print(text)  # hello

# Or use replace()
text = "Hello"
text = text.replace("H", "h")
print(text)  # hello

text = "Hello, World!"

print(text.upper())       # HELLO, WORLD!
print(text.lower())       # hello, world!
print(text.title())       # Hello, World!
print(text.capitalize())  # Hello, world!
print(text.swapcase())    # hELLO, wORLD!
print(text.casefold())    # hello, world! (aggressive lowercase)

text = "Python is awesome and Python is popular"

print(text.find("Python"))       # 0 (first occurrence index)
print(text.find("Python", 5))    # 23 (search from index 5)
print(text.find("Java"))         # -1 (not found)

print(text.rfind("Python"))      # 23 (last occurrence)
print(text.index("Python"))      # 0 (like find, but raises ValueError if not found)
print(text.count("Python"))      # 2

print(text.startswith("Python")) # True
print(text.endswith("popular"))  # True

print("Python" in text)          # True

text = "   Hello, World!   "

print(text.strip())       # "Hello, World!"
print(text.lstrip())      # "Hello, World!   "
print(text.rstrip())      # "   Hello, World!"
print(text.strip("! "))   # "Hello, World"

# Padding
num = "42"
print(num.zfill(5))           # "00042"
print(num.ljust(10, '-'))     # "42--------"
print(num.rjust(10, '-'))     # "--------42"
print(num.center(10, '-'))    # "----42----"

# Splitting
csv = "apple,banana,cherry,date"
fruits = csv.split(",")
print(fruits)  # ['apple', 'banana', 'cherry', 'date']

text = "Hello World Python"
words = text.split()  # Split on whitespace
print(words)  # ['Hello', 'World', 'Python']

# Split with maxsplit
data = "name=John=Doe"
parts = data.split("=", 1)
print(parts)  # ['name', 'John=Doe']

# Splitlines
multiline = "line1\nline2\nline3"
lines = multiline.splitlines()
print(lines)  # ['line1', 'line2', 'line3']

# Joining
words = ['Python', 'is', 'great']
sentence = " ".join(words)
print(sentence)  # "Python is great"

path = "/".join(["home", "user", "documents"])
print(path)  # "home/user/documents"

csv_line = ",".join(["Alice", "30", "Engineer"])
print(csv_line)  # "Alice,30,Engineer"

text = "Hello World World"

# Replace
print(text.replace("World", "Python"))     # Hello Python Python
print(text.replace("World", "Python", 1))  # Hello Python World

# Translate (character-level replacement)
table = str.maketrans("aeiou", "12345")
print("hello world".translate(table))  # h2ll4 w4rld

# Remove characters with translate
remove_digits = str.maketrans("", "", "0123456789")
print("abc123def456".translate(remove_digits))  # abcdef

print("hello".isalpha())      # True (only letters)
print("12345".isdigit())      # True (only digits)
print("hello123".isalnum())   # True (letters and digits)
print("   ".isspace())        # True (only whitespace)
print("Hello World".istitle()) # True (title case)
print("HELLO".isupper())      # True
print("hello".islower())      # True
print("abc123".isidentifier())# True (valid variable name)

name = "Alice"
age = 30
score = 95.5678

# Basic interpolation
print(f"Name: {name}, Age: {age}")

# Expressions
print(f"In 5 years: {age + 5}")
print(f"Uppercase: {name.upper()}")

# Number formatting
print(f"Score: {score:.2f}")         # 95.57 (2 decimal places)
print(f"Score: {score:10.2f}")       #      95.57 (10 chars wide)
print(f"Percentage: {0.856:.1%}")    # 85.6%
print(f"Big number: {1000000:,}")    # 1,000,000
print(f"Binary: {42:b}")            # 101010
print(f"Hex: {255:x}")             # ff
print(f"Oct: {8:o}")               # 10

# Alignment
print(f"{'left':<20}")    # "left                "
print(f"{'right':>20}")   # "               right"
print(f"{'center':^20}")  # "       center       "
print(f"{'padded':*^20}") # "*******padded*******"

# Debug formatting (Python 3.8+)
x = 42
print(f"{x=}")            # x=42
print(f"{x + 10=}")       # x + 10=52

# Positional arguments
print("{} is {} years old".format("Alice", 30))

# Named arguments
print("{name} is {age} years old".format(name="Alice", age=30))

# Index-based
print("{0} likes {1}. {0} is great.".format("Alice", "Python"))

# Number formatting
print("{:,.2f}".format(1234567.891))  # 1,234,567.89

# Accessing object attributes
class Point:
    def __init__(self, x, y):
        self.x = x
        self.y = y

p = Point(3, 4)
print("Point({0.x}, {0.y})".format(p))  # Point(3, 4)

# Concatenation
first = "Hello"
last = "World"
full = first + " " + last
print(full)  # Hello World

# Repetition
line = "-" * 30
print(line)  # ------------------------------

border = "+-" * 15 + "+"
print(border)  # +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

# Efficient concatenation with join (better than + in loops)
parts = []
for i in range(5):
    parts.append(f"item_{i}")
result = ", ".join(parts)
print(result)  # item_0, item_1, item_2, item_3, item_4

text = "Python"

# Iterate over characters
for char in text:
    print(char, end=" ")
# P y t h o n

# With index using enumerate
for i, char in enumerate(text):
    print(f"{i}: {char}")
# 0: P  1: y  2: t  3: h  4: o  5: n

def is_valid_number(s):
    """Check if string is a valid number (including decimals and negatives)."""
    try:
        float(s)
        return True
    except ValueError:
        return False

print(is_valid_number("42"))      # True
print(is_valid_number("3.14"))    # True
print(is_valid_number("-5"))      # True
print(is_valid_number("abc"))     # False

text = "Python is a great programming language"
word_count = len(text.split())
print(f"Word count: {word_count}")  # Word count: 6

text = "Python"
reversed_text = text[::-1]
print(reversed_text)  # nohtyP

def is_palindrome(s):
    s = s.lower().replace(" ", "")
    return s == s[::-1]

print(is_palindrome("racecar"))     # True
print(is_palindrome("A man a plan a canal Panama".replace(" ", "")))  # True