Python字符串操作完全指南

Python字符串基础操作

创建与访问

# 创建字符串
s1 = 'Hello, World!'
s2 = "Python Programming"
s3 = '''多行
字符串示例'''

# 访问字符
print(s1[0])    # H
print(s1[-1])   # !

切片操作

s = "Python is amazing!"

# 基本切片
print(s[0:6])   # Python
print(s[7:9])   # is

# 使用步长
print(s[0:12:2])  # Pto sa

# 反向切片
print(s[::-1])   # !gnizama si nohtyP

拼接与重复

# 字符串拼接
s1 = "Hello"
s2 = "World"
print(s1 + ", " + s2 + "!")  # Hello, World!

# 字符串重复
print("Ha" * 3)  # HaHaHa

# join方法高效拼接
words = ["Python", "is", "powerful"]
print(" ".join(words))  # Python is powerful

字符串格式化方法

1. % 格式化

name = "Alice"
age = 30
print("Name: %s, Age: %d" % (name, age))

2. str.format()

print("Name: {0}, Age: {1}. {0} is a programmer".format(name, age))

3. f-strings (Python 3.6+)

print(f"Name: {name}, Age: {age}. Next year: {age+1}")

常用字符串方法

大小写转换

"hello".upper()      # "HELLO"
"WORLD".lower()      # "world"
"python guide".title()  # "Python Guide"

查找与替换

"Python is fun".find('is')     # 7
"Python is fun".index('fun')   # 10
"Hello World".replace('World', 'Python')

分割与连接

"apple,banana,cherry".split(',') 
# ['apple', 'banana', 'cherry']

"-".join(['2023', '08', '01']) 
# "2023-08-01"

去除空白

"  python  ".strip()   # "python"
"  python  ".lstrip()  # "python  "
"  python  ".rstrip()  # "  python"

正则表达式应用

import re

# 查找匹配
text = "Contact: email@example.com, phone: 123-456-7890"
emails = re.findall(r'\b[A-Za-z0-9._%+-]+@[A-Za-z0-9.-]+\.[A-Z|a-z]{2,}\b', text)
# ['email@example.com']

# 替换字符串
new_text = re.sub(r'\d{3}-\d{3}-\d{4}', '[PHONE]', text)
# "Contact: email@example.com, phone: [PHONE]"

# 分割字符串
re.split(r'[,:]\s*', text)
# ['Contact', 'email@example.com', 'phone', '123-456-7890']

字符串编码与字节转换

# 字符串转字节
s = "Python编程"
b = s.encode('utf-8')  # b'Python\xe7\xbc\x96\xe7\xa8\x8b'

# 字节转字符串
b.decode('utf-8')      # "Python编程"

# 处理不同编码
with open('file.txt', 'r', encoding='utf-8') as f:
    content = f.read()