ord() Function Complexity

The ord() function returns the Unicode code point of a character.

Complexity Analysis

Case	Time	Space	Notes
Single ASCII character	O(1)	O(1)	Direct lookup
Single Unicode character	O(1)	O(1)	Direct lookup
Invalid input	O(1)	O(1)	Raises TypeError

Basic Usage

ASCII Characters

# O(1) - direct Unicode code point lookup
ord('a')       # 97
ord('A')       # 65
ord('0')       # 48
ord(' ')       # 32

Unicode Characters

# O(1) - works with any Unicode character
ord('π')       # 960
ord('€')       # 8364
ord('中')      # 20013
ord('😀')     # 128512

Special Characters

# O(1)
ord('\n')      # 10 (newline)
ord('\t')      # 9 (tab)
ord('\0')      # 0 (null)
ord('\\'')     # 92 (backslash)

Comparison with chr()

# ord() - character to code point
ord('A')       # 65

# chr() - code point to character
chr(65)        # 'A'

# Inverse operations - both O(1)
chr(ord('Z'))  # 'Z'
ord(chr(90))   # 90

Performance Patterns

Character Mapping

# O(n) - map all characters
text = "hello"
codes = [ord(c) for c in text]  # [104, 101, 108, 108, 111]

# O(n) - each ord() is O(1)
for char in text:
    code = ord(char)  # O(1) operation

Building Lookup Tables

# O(k) where k = character set size
lowercase_codes = {ord(c): c for c in "abcdefghijklmnopqrstuvwxyz"}
# {97: 'a', 98: 'b', ..., 122: 'z'}

# Useful for fast lookups
for code, char in lowercase_codes.items():
    verify = chr(code) == char  # True

Common Patterns

Sorting Characters Alphabetically

# O(1) - ord() returns comparable values
chars = ['z', 'a', 'm', 'b']
sorted_chars = sorted(chars, key=ord)
# ['a', 'b', 'm', 'z']

# But Python already sorts characters correctly
sorted_chars = sorted(chars)  # Same result, no need for ord()

Converting Text to Numbers

# O(n) - convert string to numeric codes
text = "ABC"
codes = [ord(c) for c in text]
# [65, 66, 67]

# Useful for encoding/cipher operations
def simple_cipher(text, shift=3):
    return ''.join(chr(ord(c) + shift) for c in text)

cipher_text = simple_cipher("ABC")
# "DEF"

Checking Character Type

# O(1) - check code point ranges
def is_digit_char(char):
    return ord('0') <= ord(char) <= ord('9')

is_digit_char('5')  # True
is_digit_char('a')  # False

# But use str methods instead
'5'.isdigit()  # True - clearer

Unicode Handling

Working with Unicode

# O(1) - Unicode characters
ord('é')       # 233 (Latin small e with acute)
ord('ñ')       # 241 (Latin small n with tilde)
ord('ß')       # 223 (German eszett)

# High Unicode points
ord('𝔸')       # 119808 (Mathematical Alphanumeric Symbols)
ord('🎵')      # 127925 (Music note emoji)

Character Ranges

# O(1) - check character ranges
def is_ascii(char):
    return ord(char) < 128

def is_extended_ascii(char):
    return 128 <= ord(char) < 256

def is_greek(char):
    return 0x0370 <= ord(char) <= 0x03FF

Edge Cases

Single Character Requirement

# O(1) - works only with single characters
ord('a')       # 97

# TypeError - requires single character
try:
    ord('ab')  # TypeError: ord() expected a character
except TypeError:
    pass

try:
    ord('')    # TypeError: ord() expected a character
except TypeError:
    pass

Type Requirements

# O(1) - works with strings only
ord('x')       # 120

# TypeError - not with integers
try:
    ord(120)   # TypeError
except TypeError:
    pass

Performance Considerations

vs ASCII Codes

# ord() - works with all Unicode
result = ord('€')  # 8364

# ASCII - only 0-127
import string
if ord('a') in range(128):
    print("ASCII character")

Bulk Operations

# O(n) - efficient for bulk operations
text = "hello world"
codes = [ord(c) for c in text]
# O(n) - linear time for n characters

# Using map
codes = list(map(ord, text))  # O(n) - slightly more efficient

Best Practices

✅ Do:

• Use ord() for getting character code points
• Use with chr() for bidirectional conversion
• Use map(ord, string) for bulk operations
• Use for encoding/decoding operations

❌ Avoid:

• Using ord() for character type checking (use str methods)
• Assuming ASCII-only (support Unicode)
• Passing multiple characters or strings
• Building unnecessary lookup tables

Related Functions

• chr() - Convert code point to character
• str.encode() - Convert string to bytes
• bytes.decode() - Convert bytes to string
• ord() with map() - Bulk character conversion

Version Notes

• Python 2.x: Works with Unicode strings (u"")
• Python 3.x: All strings are Unicode, ord() works seamlessly
• Python 3.8+: Same behavior, consistent Unicode support