使用python在字符串中指定字符的前面插入单个转义字符

def insert_escape_char(s, char_to_escape):
    # 先将指定字符替换为 \ 加上该字符
    s_with_escape = s.replace(char_to_escape, '\\' + char_to_escape)
    return s_with_escape

# 测试
original_string = "Hello, world! This is a test."
char_to_insert_escape_before = "s"
result = insert_escape_char(original_string, char_to_insert_escape_before)
print(result)  # 输出: Hello, world! Thi\s is a te\st.

import re

def insert_escape_char_regex(s, char_to_escape):
    # 使用正则表达式在指定字符前插入 \
    pattern = re.compile(re.escape(char_to_escape))
    s_with_escape = pattern.sub(r'\\' + char_to_escape, s)
    return s_with_escape

# 测试
original_string = "Hello, world! This is a test."
char_to_insert_escape_before = "s"
result = insert_escape_char_regex(original_string, char_to_insert_escape_before)
print(result)  # 输出: Hello, world! Thi\s is a te\st.