This chapter covers strings in Python, including their creation, properties, and various operations. Understanding strings is crucial for text manipulation and programming fundamentals.
Strings - Quick Look Revision Guide
Your 1-page summary of the most exam-relevant takeaways from Computer Science.
This compact guide covers 20 must-know concepts from Strings aligned with Class 11 preparation for Computer Science. Ideal for last-minute revision or daily review.
Complete study summary
Essential formulas, key terms, and important concepts for quick reference and revision.
Key Points
Definition of String
A string is a sequence of one or more characters. It can contain letters, digits, and symbols.
Creating Strings
Strings are created using single, double, or triple quotes. E.g., 'abc', "abc", or '''abc'''.
String Length
Use len() to get the number of characters in a string. E.g., len('Hello') returns 5.
Indexing
Characters in strings can be accessed via indexing, starting from 0 to n-1, and -1 to -n for reverse.
Immutable Nature
Strings are immutable; you cannot change their content after creation, e.g., str[1] = 'a' causes TypeError.
Concatenation
Join strings using the '+' operator. E.g., 'Hello' + 'World' gives 'HelloWorld'.
Repetition
Repeat a string using the '*' operator. E.g., 'Hello' * 3 produces 'HelloHelloHello'.
Membership Operators
Use 'in' to check substring presence, e.g., 'world' in 'Hello world!' returns True.
Slicing
Extract parts of strings using slices, e.g., str[1:5] returns 'ello' from 'Hello'.
Negative Indexing
Use negative indices to access characters from the end of a string. E.g., str[-1] returns the last character.
String Iteration
Traverse strings using loops. E.g., for ch in str: print(ch) iterates through each character.
Common String Methods
Methods like title(), lower(), and upper() format strings by changing case.
Finding Substrings
Use find() to locate the first occurrence of a substring. Returns -1 if not found.
Replacing Text
Use replace(old, new) to replace old substrings with new in the string.
String Splitting
Use split() to divide a string into a list of words. Str.split(' ') splits by spaces.
Joining Strings
Use join() to concatenate list elements into a single string with a separator, e.g., '-'.join(list).
Checking Start/End
startswith() and endswith() check if strings begin or end with specific substrings.
Whitespace Handling
Methods like strip(), lstrip(), and rstrip() remove whitespace from different sides of a string.
String Comparison
Compare strings using relational operators. E.g., 'abc' < 'abd' is True.
Palindromes
A string is a palindrome if it reads the same forwards as backwards, e.g., 'radar'.
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