Python 字符串

# 使用单引号
str1 = 'Hello World'
# 使用双引号
str2 = "Python Programming"
# 使用三引号（可以包含多行）
str3 = '''这是一个
多行字符串
示例'''

text = "Python"
# 访问单个字符
print(text[0])    # 输出: P
print(text[-1])   # 输出: n
# 字符串切片
print(text[0:3])  # 输出: Pyt

text = "hello world"
# 转换为大写
print(text.upper())      # 输出: HELLO WORLD
# 转换为小写
print(text.lower())      # 输出: hello world
# 首字母大写
print(text.capitalize()) # 输出: Hello world
# 每个单词首字母大写
print(text.title())      # 输出: Hello World

text = "Python is awesome"
# 查找子字符串
print(text.find("is"))      # 输出: 7
print(text.count("o"))      # 输出: 2
# 替换字符串
print(text.replace("awesome", "great"))  # 输出: Python is great

# 分割字符串
text = "Python,Java,C++"
languages = text.split(",")  # 输出: ['Python', 'Java', 'C++']

# 连接字符串
words = ['Hello', 'World']
sentence = " ".join(words)   # 输出: Hello World

name = "Alice"
age = 25
print(f"{name} is {age} years old")

name = "Bob"
age = 30
print("{} is {} years old".format(name, age))

name = "Charlie"
age = 35
print("%s is %d years old" % (name, age))

# 连接操作符 +
str1 = "Hello"
str2 = "World"
print(str1 + " " + str2)  # 输出: Hello World

# 重复操作符 *
print(str1 * 3)  # 输出: HelloHelloHello

# 成员操作符 in
print("He" in str1)  # 输出: True

# 常用转义字符
print("First line\nSecond line")  # 换行
print("Tab\tspacing")             # 制表符
print("Backslash\\")              # 反斜杠
print("Single quote\'")           # 单引号
print("Double quote\"")           # 双引号

text = "Hello"
# text[0] = "h"  # 这会引发错误
# 正确的方式是创建新的字符串
text = "h" + text[1:]  # 输出: hello

# 字符串编码
text = "你好"
encoded = text.encode('utf-8')
print(encoded)  # 输出: b'\xe4\xbd\xa0\xe5\xa5\xbd'

# 字符串解码
decoded = encoded.decode('utf-8')
print(decoded)  # 输出: 你好