Built-In functions and Methods
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String Built-In Functions: len(), chr(), ord(), str()
1. len():it returns the length of a string
```
s = "hello"
print(len(s)) # 5
```
2. chr(): it Converts Unicode number to character
```
print(chr(65)) # A
print(chr(128512)) # 😀
```
3. ord(): it Converts character to Unicode number
```
print(ord('A')) # 65
print(ord('😊')) # 128522
```
4. str():it Converts object to string
```
print(str(123)) # '123'
print(str(3.14)) # '3.14'
```
String Methods
Below are the most important Python string methods explained with clear examples.
1. capitalize():Converts the first character to uppercase and the rest to lowercase.
```
print("python programming".capitalize())
# Python programming
```
2. casefold():Converts string into aggressive lowercase for case-insensitive comparisons.
Aggressive lowercase (useful for comparisons).
```
print("ß".casefold()) # ss
```
3. center(width): Returns the string centered in a field of given width with optional fill character.
```
print("hello".center(20, '*'))
```
4. count():Returns the number of occurrences of a substring.
```
print("banana".count("a")) # 3
```
5. encode():Converts the string into a bytes object using the given encoding.
```
print("hello".encode("utf-8"))
# b'hello'
```
6. endswith():Checks if the string ends with the specified suffix.
```
print("notes.pdf".endswith(".pdf")) # True
```
7. find():Returns the index of the first occurrence of a substring or -1 if not found. Returns index or -1.
```
print("hello".find("l")) # 2
```
8. format():Inserts values into placeholders {} using the format specification.
```
print("Hello {}".format("Megha"))
```
9. index():Returns index of substring but raises an error if not found. Like find() but raises error if not found.
```
print("hello".index("e")) # 1
```
10. isalnum(), isalpha(), isdigit(), isnumeric(), isspace()
Returns True if all characters are alphanumeric.
- isalpha(): True if all characters are alphabets
- isdigit(): True if all characters are digits.
- isnumeric(): True if characters are numeric (including unicode numbers).
- isspace(): True if string contains only whitespace characters.
```
"abc123".isalnum() # True
"abc".isalpha() # True
"123".isdigit() # True
" ".isspace() # True
```
11. join():Joins items of an iterable into a single string separated by the current string.
```
names = ["A", "B", "C"]
print("-".join(names))
# A-B-C
```
12. lower(), upper(), title(), capitalize():Converts string to lowercase / uppercase / title case / capitalized case.
```
s = "hello world"
print(s.upper()) # HELLO WORLD
print(s.title()) # Hello World
```
13. lstrip(), rstrip(), strip():Removes leading / trailing / both-side whitespace (or specified characters).
```
print(" hello ".strip()) # hello
```
14. partition():Splits string into a tuple: (before sep, sep, after sep).
```
print("a-b-c".partition("-"))
# ('a', '-', 'b-c')
```
15. replace():Replaces all occurrences of a substring with another substring.
```
print("hello world".replace("world", "Python"))
```
16. rfind():Returns the last occurrence index of a substring or -1 if not found.
```
print("hello".rfind("l")) # 3
```
17. split():Splits string into a list based on a separator.
```
print("a,b,c".split(","))
# ['a', 'b', 'c']
```
18. splitlines():Splits the string at line breaks into a list of lines.
```
print("A\nB\nC".splitlines())
# ['A', 'B', 'C']
```
19. startswith():Checks if the string begins with the specified prefix.
```
print("python".startswith("py"))
```
20. swapcase():Swaps uppercase characters to lowercase and vice-versa.
```
print("HeLLo".swapcase()) # hEllO
```
21. zfill():Pads the string on the left with zeros to reach the given width.
```
print("42".zfill(5)) # 00042
```
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