Summary of Strings in Python - Advanced Python 05 - Programming Tutorial

Main Ideas and Concepts

• Definition of Strings: Strings are ordered, immutable collections of characters used for text representation in Python.
• Creating Strings: Strings can be created using single quotes (') or double quotes ("). Triple quotes (''' or """) are used for multi-line Strings and documentation.
• String Indexing and Slicing: Strings can be indexed like lists, starting from 0 for the first character. Negative Indexing allows access to characters from the end of the string. Slicing is used to obtain substrings using the syntax my_string[start:stop].
• String Concatenation: Strings can be concatenated using the + operator.
• Iterating Over Strings: Strings can be iterated using a for loop.
• Membership Testing: The in keyword checks if a character or substring exists within a string.
• String Methods: Common String Methods include:
  • .strip(): Removes whitespace from both ends.
  • .upper(): Converts all characters to uppercase.
  • .lower(): Converts all characters to lowercase.
  • .startswith(): Checks if a string starts with a specified substring.
  • .endswith(): Checks if a string ends with a specified substring.
  • .find(): Returns the index of the first occurrence of a substring.
  • .count(): Counts occurrences of a character or substring.
  • .replace(): Replaces occurrences of a substring with another substring.
  • .split(): Splits a string into a list based on a delimiter.
  • ''.join(): Joins elements of a list into a string.
• Performance Considerations: Using ''.join() is preferred over Concatenation in a loop for performance reasons.
• String Formatting: Three methods of formatting Strings:
  • Old Style: Using the % operator.
  • Format Method: Using the .format() method.
  • F-Strings: Introduced in Python 3.6, using f"" syntax for inline variable evaluation.

Detailed Bullet Point Instructions

• Creating Strings:
  • Use single or double quotes: my_string = "Hello, World!"
  • For Strings with quotes inside, escape them or use different quotes: valid_string1 = 'I\'m a programmer' valid_string2 = "I'm a programmer"
• Accessing Characters:
  • Use Indexing: first_char = my_string[0] # 'H'
  • last_char = my_string[-1] # '!'
• Slicing Strings:
  • Basic slicing: substring = my_string[1:5] # 'ello'
  • Slicing with step: every_second_char = my_string[::2] # 'Hlo ol!'
• Concatenating Strings:
  • Use +: full_greeting = greeting + " " + name # 'Hello Tom'
• Iterating Over Strings:
  • Example: for char in my_string: print(char)
• Using String Methods:
  • Removing whitespace: cleaned_string = my_string.strip()
  • Changing case: upper_case = my_string.upper()
  • Finding substrings: index = my_string.find("World") # Returns index of 'W'
• Joining a List into a String:
  • Using join(): joined_string = ' '.join(my_list) # 'Hello World'
• String Formatting:
  • Old style: formatted_string = "Hello, %s" % name
  • Format method: formatted_string = "Hello, {}".format(name)
  • F-Strings: formatted_string = f"Hello, {name}"

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