02_strings_tutorial.py

# 1. Creating strings
# Strings can be created with single or double quotes
single = 'Hello'
double = "World"
multiline = """This is
a multiline
string"""

print(single, double)
print(multiline)

# 2. String concatenation (joining)
first_name = "Pavel"
last_name = "Ivanov"
full_name = first_name + " " + last_name
print(f"Full name: {full_name}")

# 3. String formatting (f-strings - the most modern way)
age = 25
message = f"My name is {first_name}, I am {age} years old"
print(message)

# With expressions inside
print(f"In 5 years I will be {age + 5} years old")

# 4. String indexing (accessing characters)
text = "Python"
print(f"First character: {text[0]}")      # P
print(f"Last character: {text[-1]}")      # n
print(f"Second from end: {text[-2]}")     # o

# 5. String slicing
text = "Hello, World!"
print(f"First 5 characters: {text[0:5]}")    # Hello
print(f"From 7th to end: {text[7:]}")        # World!
print(f"Last 6 characters: {text[-6:]}")     # World!
print(f"Every second character: {text[::2]}") # Hlo ol!
print(f"String reversed: {text[::-1]}")      # !dlroW ,olleH

# 6. String methods (main ones)
sample = "  python programming  "

# Removing whitespace
print(f"strip(): '{sample.strip()}'")           # removes spaces from both sides
print(f"lstrip(): '{sample.lstrip()}'")         # from left
print(f"rstrip(): '{sample.rstrip()}'")         # from right

# Changing case
text = "Python"
print(f"upper(): {text.upper()}")               # PYTHON
print(f"lower(): {text.lower()}")               # python
print(f"capitalize(): {text.capitalize()}")     # Python
print(f"title(): 'hello world'.title()")        # Hello World

# Search and replace
sentence = "I learn Python. Python is a great language!"
print(f"count('Python'): {sentence.count('Python')}")  # 2
print(f"find('Python'): {sentence.find('Python')}")    # 7 (index of first occurrence)
print(f"replace(): {sentence.replace('Python', 'JS')}")

# Checks
print(f"'Python'.isalpha(): {'Python'.isalpha()}")     # True (only letters)
print(f"'123'.isdigit(): {'123'.isdigit()}")           # True (only digits)
print(f"'Py123'.isalnum(): {'Py123'.isalnum()}")       # True (letters and digits)

# 7. Splitting and joining strings
csv = "apple,banana,orange"
fruits = csv.split(',')
print(f"split(','): {fruits}")

joined = " - ".join(fruits)
print(f"join(): {joined}")

# 8. Checking substring presence
text = "Python for beginners"
print(f"'Python' in text: {'Python' in text}")          # True
print(f"'Java' not in text: {'Java' not in text}")      # True

# 9. String length
text = "Hello"
print(f"len('{text}'): {len(text)}")  # 5

# 10. Escaping special characters
# \n - newline, \t - tab, \\ - backslash, \' - single quote
escaped = "String with \nnewline and \ttab"
print(escaped)

# Raw-strings (don't interpret escape sequences)
path = r"C:\users\name\documents"
print(path)