1def escape(text, special_chars, escape_char='\\'):
2    """Escape special characters by prefixing with escape_char."""
3    result = []
4    for char in text:
5        if char == escape_char or char in special_chars:
6            result.append(escape_char)
7        result.append(char)
8    return ''.join(result)
9
10def unescape(text, escape_char='\\'):
11    """Remove escape prefixes, restoring original characters."""
12    result = []
13    i = 0
14    while i < len(text):
15        if text[i] == escape_char and i + 1 < len(text):
16            result.append(text[i + 1])  # Take the next char literally
17            i += 2
18        else:
19            result.append(text[i])
20            i += 1
21    return ''.join(result)
22
23# Example
24original = 'price is $10 (50% off)'
25escaped = escape(original, special_chars={'$', '(', ')', '%'})
26print(escaped)   # price is \$10 \(50\% off\)
27print(unescape(escaped))  # price is $10 (50% off)

1original = r'path\to\file'
2escaped = escape(original, special_chars=set())  # No special chars, but \ is always escaped
3print(escaped)   # path\\to\\file
4print(unescape(escaped))  # path\to\file

1# Built-in escaping for strings
2text = 'She said "hello"'
3escaped = text.replace('"', '\\"')
4# She said \"hello\"
5
6# For regex special characters
7import re
8pattern = re.escape('price is $10.00 (USD)')
9# price\ is\ \$10\.00\ \(USD\)
10
11# For SQL (use parameterized queries instead)
12# cursor.execute("SELECT * FROM users WHERE name = %s", (user_input,))

1// Escape HTML special characters
2function escapeHtml(text) {
3    const map = {
4        '&': '&',
5        '<': '&lt;',
6        '>': '&gt;',
7        '"': '&quot;',
8        "'": '&#039;'
9    };
10    return text.replace(/[&<>"']/g, char => map[char]);
11}
12
13// Escape regex special characters
14function escapeRegex(string) {
15    return string.replace(/[.*+?^${}()|[\]\\]/g, '\\$&');
16}
17
18// Escape for JSON strings
19const escaped = JSON.stringify("line1\nline2");
20// "\"line1\\nline2\""

1// Backslash escaping in string literals
2char *str = "She said \"hello\"";    // She said "hello"
3char *path = "C:\\Users\\file.txt";  // C:\Users\file.txt
4char *newline = "line1\nline2";      // line1<newline>line2

1-- Escape single quotes by doubling them
2SELECT * FROM users WHERE name = 'O''Brien';
3
4-- MySQL: backslash escaping
5SELECT * FROM users WHERE name = 'O\'Brien';
6
7-- Best practice: use parameterized queries instead of manual escaping

1from urllib.parse import quote, unquote
2
3text = "hello world & foo=bar"
4encoded = quote(text)
5print(encoded)   # hello%20world%20%26%20foo%3Dbar
6print(unquote(encoded))  # hello world & foo=bar

1import html
2
3text = '<script>alert("xss")</script>'
4escaped = html.escape(text)
5print(escaped)  # &lt;script&gt;alert(&quot;xss&quot;)&lt;/script&gt;
6print(html.unescape(escaped))  # <script>alert("xss")</script>