Python: String Special Operators

# The + operator joins two or more strings together

# 1. Simple concatenation
first = "Hello"
second = "World"
result = first + " " + second
print(result)  # Hello World

# 2. Concatenating multiple strings
greeting = "Hi"
name = "Alice"
message = greeting + ", " + name + "!"
print(message)  # Hi, Alice!

# 3. Concatenating strings with numbers
age = 25
text = "I am " + str(age) + " years old"
print(text)  # I am 25 years old

# 4. Concatenating strings in a loop
words = ["Python", "is", "awesome"]
sentence = ""
for word in words:
    sentence += word + " "
print(sentence.strip())  # Python is awesome

# 5. Using join() for multiple strings (more efficient)
words = ["Python", "is", "awesome"]
sentence = " ".join(words)
print(sentence)  # Python is awesome

# 6. Adjacent string literals (Python automatically joins)
text = "Hello" " " "World"
print(text)  # Hello World

# The * operator repeats a string a specified number of times

# 1. Basic repetition
text = "Ha"
print(text * 3)  # HaHaHa

# 2. Creating lines
line = "-" * 40
print(line)
print("Section Header")
print(line)

# 3. Creating patterns
pattern = "* " * 10
print(pattern)  # * * * * * * * * * *

# 4. Repeating with variables
repeat = 5
print("Hello " * repeat)  # Hello Hello Hello Hello Hello

# 5. Repeating zero times (empty string)
print("Test" * 0)  # (nothing prints)

# 6. Practical: Progress bar
def show_progress(percentage):
    filled = "█" * (percentage // 10)
    empty = "░" * (10 - (percentage // 10))
    return f"{filled}{empty} {percentage}%"

print(show_progress(30))  # ███░░░░░░░ 30%
print(show_progress(70))  # ███████░░░ 70%

# 7. Creating a simple table row
row = "+" + "-" * 10 + "+" + "-" * 10 + "+"
print(row)

# Slicing lets you extract a portion of a string

text = "Python Programming"

# 1. Basic slicing
print(text[0:6])   # Python
print(text[7:18])  # Programming
print(text[:6])    # Python (from start to index 5)
print(text[7:])    # Programming (from index 7 to end)

# 2. Slicing with negative indices
print(text[-11:])  # Programming
print(text[-6:-1]) # rammi

# 3. Slicing with step
word = "abcdefghij"
print(word[::2])   # acegi (every second)
print(word[1::2])  # bdfhj (every second from index 1)
print(word[::-1])  # jihgfedcba (reversed)

# 4. Practical: Getting file extension
filename = "document.pdf"
extension = filename[filename.index("."):]
print(extension)  # .pdf

# 5. Practical: Getting domain from email
email = "user@example.com"
domain = email[email.index("@")+1:]
print(domain)  # example.com

# 6. Reversing a string
word = "Python"
reversed_word = word[::-1]
print(reversed_word)  # nohtyP

# The 'in' and 'not in' operators check if text exists in a string

# 1. Basic membership
text = "Python is awesome"
print("Python" in text)    # True
print("Java" in text)      # False

# 2. Using not in
print("Java" not in text)  # True
print("Python" not in text) # False

# 3. Checking for characters
word = "Hello"
print("e" in word)  # True
print("z" in word)  # False

# 4. Practical: Email validation
email = "user@example.com"
if "@" in email and "." in email:
    print("Valid email format")

# 5. Practical: Filtering words
words = ["apple", "banana", "cherry", "date"]
filtered = [w for w in words if "a" in w]
print(filtered)  # ['apple', 'banana', 'date']

# 6. Case sensitivity (lowercase matters)
text = "Hello"
print("hello" in text)  # False (case-sensitive)

# 7. Checking multiple conditions
username = "alice123"
if any(char.isdigit() for char in username):
    print("Username contains a number")

# Strings can be compared alphabetically using comparison operators

# 1. Equality and inequality
print("hello" == "hello")  # True
print("hello" == "world")  # False
print("hello" != "world")  # True

# 2. Lexicographic comparison (alphabetical order)
print("apple" < "banana")   # True (a comes before b)
print("apple" > "banana")   # False
print("apple" <= "apple")   # True

# 3. Case sensitivity (uppercase comes before lowercase)
print("Apple" < "apple")   # True (A comes before a in ASCII)
print("Zebra" < "apple")   # True (Z comes before a)

# 4. String length comparison
print("abc" < "abcd")  # True (shorter string is smaller)

# 5. Practical: Sorting names
names = ["Charlie", "Alice", "Bob"]
sorted_names = sorted(names)
print(sorted_names)  # ['Alice', 'Bob', 'Charlie']

# 6. Practical: Case-insensitive comparison
def is_same_ignore_case(str1, str2):
    return str1.lower() == str2.lower()

print(is_same_ignore_case("Hello", "HELLO"))  # True

# The % operator is the old style of string formatting
# It's still used in some older code, so it's good to know

# 1. Basic formatting
name = "Alice"
age = 25
message = "Hello, %s! You are %d years old." % (name, age)
print(message)  # Hello, Alice! You are 25 years old.

# 2. Format specifiers
# %s - string
# %d - integer
# %f - float
# %.2f - float with 2 decimal places

name = "Bob"
score = 85.5
text = "Name: %s, Score: %.2f" % (name, score)
print(text)  # Name: Bob, Score: 85.50

# 3. Multiple placeholders
item = "book"
price = 19.99
quantity = 3
total = price * quantity
order = "Item: %s, Price: $%.2f, Quantity: %d, Total: $%.2f" % (item, price, quantity, total)
print(order)  # Item: book, Price: $19.99, Quantity: 3, Total: $59.97

# 4. Formatting with dictionary
data = {"name": "Charlie", "age": 30}
print("Name: %(name)s, Age: %(age)d" % data)  # Name: Charlie, Age: 30

# 5. Padding and alignment
print("%10s" % "Hello")   # "     Hello" (right aligned)
print("%-10s" % "Hello")  # "Hello     " (left aligned)
print("%05d" % 42)        # "00042" (zero padding)