106 lines
2.9 KiB
Python
106 lines
2.9 KiB
Python
# 第 1-7 课示例：字符串
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#
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# 本文件集中演示字符串索引、切片、遍历和常见方法。
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# 建议运行后对照每段注释观察结果，不需要用户输入。
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# 一、索引
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# 正索引从 0 开始，负索引从 -1 开始倒数。
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technology = "Python"
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print(f"第一个字符：{technology[0]}")
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print(f"最后一个字符：{technology[-1]}")
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# 二、长度
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# 空格和标点同样会计入字符串长度。
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prompt = "Python Agent"
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print(f"提示词长度：{len(prompt)}")
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# 三、切片
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# 切片包含开始索引，不包含结束索引。
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print(f"前三个字符：{technology[0:3]}")
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print(f"从索引 3 到末尾：{technology[3:]}")
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print(f"反转字符串：{technology[::-1]}")
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# 四、遍历字符串
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# for 会依次取得字符串中的每一个字符。
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for character in "Agent":
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print(f"当前字符：{character}")
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# 五、清理两侧空白并转换大小写
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raw_text = " Python Agent "
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clean_text = raw_text.strip()
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lower_text = clean_text.lower()
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upper_text = clean_text.upper()
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print(f"清理结果：{clean_text}")
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print(f"小写结果：{lower_text}")
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print(f"大写结果：{upper_text}")
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# 六、替换文本
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# replace() 返回新字符串，不会直接修改原字符串。
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old_goal = "学习 Java 开发"
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new_goal = old_goal.replace("Java", "Python")
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print(f"原目标：{old_goal}")
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print(f"新目标：{new_goal}")
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# 七、查找和统计
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analysis_text = "Python Agent Python FastAPI"
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contains_agent = "Agent" in analysis_text
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python_position = analysis_text.find("Python")
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python_count = analysis_text.count("Python")
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print(f"是否包含 Agent：{contains_agent}")
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print(f"Python 首次出现位置：{python_position}")
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print(f"Python 出现次数：{python_count}")
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# 八、判断开头与结尾
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file_name = "agent_service.py"
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print(f"是否以 agent 开头：{file_name.startswith('agent')}")
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print(f"是否为 Python 文件：{file_name.endswith('.py')}")
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# 九、分割与连接
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# split() 得到列表；列表将在下一课系统学习。
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technology_text = "Python,FastAPI,Django"
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technology_list = technology_text.split(",")
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technology_path = " -> ".join(technology_list)
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print(f"分割结果：{technology_list}")
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print(f"连接结果：{technology_path}")
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# 十、字符串判断方法
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age_text = "18"
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code_text = "Agent2026"
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print(f"年龄是否全部为数字：{age_text.isdigit()}")
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print(f"代码是否只包含字母和数字：{code_text.isalnum()}")
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# 十一、方法链
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# 先清理两侧空白，再统一转为小写。
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raw_answer = " YES "
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clean_answer = raw_answer.strip().lower()
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print(f"标准化回答：{clean_answer}")
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# 十二、转义字符和原始字符串
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print("第一行\n第二行")
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project_path = r"D:\Code\Python"
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print(f"项目路径：{project_path}")
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# 十三、f-string 数字格式
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total_hours = 6.5
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progress = 0.756
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print(f"总时长：{total_hours:.2f} 小时")
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print(f"完成率：{progress:.1%}")
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