python中的str是什么意思 python字符串类型说明

# 单引号和双引号定义的字符串
single_quoted = 'Hello, World!'
double_quoted = "Hello, World!"

# 三引号定义的多行字符串
multi_line = """This is a multi-line
string in Python."""

# 字符串是不可变的
original = "Hello"
# 以下操作会生成一个新的字符串
modified = original + ", World!"
print(modified)  # 输出: Hello, World!

# 字符串拼接
greeting = "Hello"
name = "Alice"
message = greeting + ", " + name
print(message)  # 输出: Hello, Alice

# 字符串切片
text = "Python is awesome"
print(text[0:6])  # 输出: Python
print(text[-7:])  # 输出: awesome

# 查找子串
index = text.find("is")
print(index)  # 输出: 7

# 替换子串
new_text = text.replace("awesome", "fantastic")
print(new_text)  # 输出: Python is fantastic

# 大小写转换
text = "Hello, World!"
print(text.lower())  # 输出: hello, world!
print(text.upper())  # 输出: HELLO, WORLD!

# 去除首尾空白
whitespace = "  Hello, World!  "
print(whitespace.strip())  # 输出: Hello, World!

# 拆分字符串
sentence = "The quick brown fox jumps over the lazy dog"
words = sentence.split()
print(words)  # 输出: ['The', 'quick', 'brown', 'fox', 'jumps', 'over', 'the', 'lazy', 'dog']

# 连接字符串
joined = "-".join(words)
print(joined)  # 输出: The-quick-brown-fox-jumps-over-the-lazy-dog

import re

text = "The price is $100"
# 使用正则表达式提取数字
match = re.search(r'\$(\d+)', text)
if match:
    price = match.group(1)
    print(price)  # 输出: 100

# 优化字符串拼接
words = ["Hello", "World", "Python"]
# 使用 join() 方法拼接
result = " ".join(words)
print(result)  # 输出: Hello World Python

# 在循环中处理字符串
lines = []
for i in range(1000):
    lines.append(f"Line {i}")
# 使用 join() 方法拼接
text = "\n".join(lines)
print(text[:50])  # 输出前50个字符