Cheat sheet · Class 11 · CBSE · Science Computer Science
Strings cheat sheet
The whole chapter on one page: key formulas, facts and the points to remember, for quick revision before a test.
CBSE Class 11 · Computer Science
Cheat sheet
Chapter 8Strings
Strings are immutable — every ‘change’ makes a new string.
1. Indexing & Slicing
- Indices 0 … n-1 forward, -1 … -n backward.
- s[start:stop:step] — stop excluded.
- s[::-1] reverses a string.
s = 'PYTHON' → s[1:4] = 'YTH', s[-2:] = 'ON'
2. Operations
- Concatenation +, repetition *.
- Membership: 'a' in s.
- Traversal with for ch in s.
3. Common Methods
| Method | Does |
|---|---|
| len(s) | length |
| upper(), lower(), title(), capitalize() | change case |
| find(sub), index(sub), count(sub) | search / count |
| isalpha(), isdigit(), isalnum(), isspace() | tests |
| strip(), lstrip(), rstrip() | remove spaces |
| split(), join(), replace(), partition() | split / combine |
| startswith(), endswith() | prefix / suffix check |
4. Key Points
- find() returns -1 if absent; index() raises an error.
- s[0] = 'x' is an error (immutable).
- Strings compare by Unicode values.
- Triple quotes for multi-line strings.
Remember: Indexing & slicing | immutable | key methods
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