python# 字符串转整数num_str = "123"num_int = int(num_str)print(num_int, type(num_int))  # 输出: 123 <class 'int'># 浮点数转整数（截断小数部分）float_num = 3.14int_num = int(float_num)print(int_num)  # 输出: 3# 布尔值转整数true_val = Truefalse_val = Falseprint(int(true_val), int(false_val))  # 输出: 1 0# 二进制、八进制、十六进制字符串转十进制整数binary_str = "0b1010"octal_str = "0o12"hex_str = "0xA"print(int(binary_str, 2))  # 输出: 10print(int(octal_str, 8))   # 输出: 10print(int(hex_str, 16))    # 输出: 10

python# 字符串转浮点数float_str = "3.14"num_float = float(float_str)print(num_float, type(num_float))  # 输出: 3.14 <class 'float'># 整数转浮点数int_num = 42float_num = float(int_num)print(float_num)  # 输出: 42.0# 布尔值转浮点数print(float(True), float(False))  # 输出: 1.0 0.0# 科学计数法字符串转浮点数sci_str = "1.23e-4"print(float(sci_str))  # 输出: 0.000123

python# 数字转字符串num = 123str_num = str(num)print(str_num, type(str_num))  # 输出: 123 <class 'str'># 布尔值转字符串bool_val = Trueprint(str(bool_val))  # 输出: 'True'# 列表转字符串（需要额外处理）my_list = [1, 2, 3]list_str = str(my_list)print(list_str)  # 输出: '[1, 2, 3]'# 更优雅的列表转字符串方式better_list_str = ", ".join(map(str, my_list))print(better_list_str)  # 输出: '1, 2, 3'

python# 数值转布尔值print(bool(0), bool(1), bool(-1))  # 输出: False True Trueprint(bool(0.0), bool(3.14))       # 输出: False True# 空序列转布尔值print(bool(""), bool([]), bool(()), bool({}))  # 输出: False False False False# None转布尔值print(bool(None))  # 输出: False# 非空值转布尔值print(bool("hello"), bool([1]), bool({"a": 1}))  # 输出: True True True

python# 字符串转列表（分割字符串）str_data = "apple,banana,orange"list_from_str = str_data.split(",")print(list_from_str)  # 输出: ['apple', 'banana', 'orange']# 元组转列表my_tuple = (1, 2, 3)list_from_tuple = list(my_tuple)print(list_from_tuple)  # 输出: [1, 2, 3]# 集合转列表my_set = {1, 2, 3}list_from_set = list(my_set)print(list_from_set)  # 输出: [1, 2, 3] (顺序可能不同)# 字典转列表（获取键、值或键值对）my_dict = {"a": 1, "b": 2}keys_list = list(my_dict.keys())values_list = list(my_dict.values())items_list = list(my_dict.items())print(keys_list, values_list, items_list)# 输出: ['a', 'b'] [1, 2] [('a', 1), ('b', 2)]

python# 列表转元组my_list = [1, 2, 3]tuple_from_list = tuple(my_list)print(tuple_from_list)  # 输出: (1, 2, 3)# 字符串转元组（单个字符）str_data = "hello"tuple_from_str = tuple(str_data)print(tuple_from_str)  # 输出: ('h', 'e', 'l', 'l', 'o')# 集合转元组my_set = {1, 2, 3}tuple_from_set = tuple(my_set)print(tuple_from_set)  # 输出: (1, 2, 3) (顺序可能不同)

python# 列表转集合（自动去重）my_list = [1, 2, 2, 3, 4, 4]set_from_list = set(my_list)print(set_from_list)  # 输出: {1, 2, 3, 4}# 字符串转集合（单个字符）str_data = "mississippi"set_from_str = set(str_data)print(set_from_str)  # 输出: {'i', 'm', 'p', 's'}# 元组转集合my_tuple = (1, 2, 2, 3)set_from_tuple = set(my_tuple)print(set_from_tuple)  # 输出: {1, 2, 3}

python# 两个列表转字典（键值对）keys = ["a", "b", "c"]values = [1, 2, 3]dict_from_lists = dict(zip(keys, values))print(dict_from_lists)  # 输出: {'a': 1, 'b': 2, 'c': 3}# 元组列表转字典tuple_list = [("a", 1), ("b", 2), ("c", 3)]dict_from_tuples = dict(tuple_list)print(dict_from_tuples)  # 输出: {'a': 1, 'b': 2, 'c': 3}# 字典键或值转集合my_dict = {"a": 1, "b": 2, "c": 3}keys_set = set(my_dict.keys())values_set = set(my_dict.values())print(keys_set, values_set)  # 输出: {'a', 'b', 'c'} {1, 2, 3}

pythonimport json# Python字典转JSON字符串data_dict = {"name": "Alice", "age": 25, "city": "New York"}json_str = json.dumps(data_dict)print(json_str)  # 输出: {"name": "Alice", "age": 25, "city": "New York"}# JSON字符串转Python字典parsed_dict = json.loads(json_str)print(parsed_dict)  # 输出: {'name': 'Alice', 'age': 25, 'city': 'New York'}# 处理日期等特殊对象（需要自定义序列化）from datetime import datetimedef default_serializer(obj):if isinstance(obj, datetime):return obj.isoformat()raise TypeError("Type not serializable")data_with_date = {"event": "conference", "date": datetime.now()}json_str_with_date = json.dumps(data_with_date, default=default_serializer)print(json_str_with_date)

python# 字符串转字节str_data = "Hello, 世界"bytes_data = str_data.encode("utf-8")print(bytes_data)  # 输出: b'Hello, \xe4\xb8\x96\xe7\x95\x8c'# 字节转字符串decoded_str = bytes_data.decode("utf-8")print(decoded_str)  # 输出: Hello, 世界# 处理不同编码gbk_bytes = str_data.encode("gbk")print(gbk_bytes)  # 输出: b'Hello, \xca\xc0\xbd\xe7'gbk_decoded = gbk_bytes.decode("gbk")print(gbk_decoded)  # 输出: Hello, 世界

pythonclass Person:def __init__(self, name, age):self.name = nameself.age = agedef __repr__(self):return f"Person(name='{self.name}', age={self.age})"# 自定义对象转字典（简单实现）def person_to_dict(person):return {"name": person.name, "age": person.age}p = Person("Bob", 30)p_dict = person_to_dict(p)print(p_dict)  # 输出: {'name': 'Bob', 'age': 30}# 更通用的方法（使用__dict__）class BetterPerson:def __init__(self, name, age, city):self.name = nameself.age = ageself.city = citydef to_dict(self):return self.__dict__.copy()bp = BetterPerson("Alice", 25, "London")bp_dict = bp.to_dict()print(bp_dict)  # 输出: {'name': 'Alice', 'age': 25, 'city': 'London'}

python# 处理无效的字符串转换def safe_int_conversion(value):try:return int(value)except (ValueError, TypeError):return None  # 或者返回默认值，或者抛出自定义异常print(safe_int_conversion("123"))  # 输出: 123print(safe_int_conversion("abc"))  # 输出: Noneprint(safe_int_conversion(None))   # 输出: None# 更健壮的浮点数转换def safe_float_conversion(value):if value is None:return 0.0try:return float(value)except ValueError:try:# 尝试处理带有千位分隔符的数字if isinstance(value, str):value = value.replace(",", "")return float(value)except ValueError:return 0.0print(safe_float_conversion("1,234.56"))  # 输出: 1234.56print(safe_float_conversion("abc"))       # 输出: 0.0

python# 使用isinstance()而不是type()进行类型检查def process_value(value):if isinstance(value, (int, float)):print(f"Processing numeric value: {value}")elif isinstance(value, str):print(f"Processing string: '{value}'")elif isinstance(value, (list, tuple, set)):print(f"Processing sequence with {len(value)} items")else:print(f"Unknown type: {type(value)}")process_value(42)process_value("hello")process_value([1, 2, 3])process_value({"a": 1})

pythonimport timeit# 比较不同转换方法的性能list_data = list(range(10000))def tuple_conversion_1():return tuple(list_data)def tuple_conversion_2():t = ()for item in list_data:t += (item,)return t# 测试性能time1 = timeit.timeit(tuple_conversion_1, number=1000)time2 = timeit.timeit(tuple_conversion_2, number=1000)print(f"tuple()方法耗时: {time1:.6f}秒")print(f"循环拼接方法耗时: {time2:.6f}秒")# 通常tuple()内置方法比循环拼接快得多

pythonimport ast# 安全地评估包含Python字面量的字符串safe_str = "[1, 2, 3]"unsafe_str = "os.system('rm -rf /')"  # 危险操作try:# 比eval（)安全，只评估字面量parsed = ast.literal_eval（safe_str)print(parsed)  # 输出: [1, 2, 3]# 这会抛出ValueError异常# ast.literal_eval（unsafe_str)except (ValueError, SyntaxError) as e:print(f"安全评估失败: {e}")

pythonimport pandas as pd# 字典列表转DataFramedata = [{"name": "Alice", "age": 25, "city": "New York"},{"name": "Bob", "age": 30, "city": "Chicago"},{"name": "Charlie", "age": 35, "city": "Los Angeles"}]df = pd.DataFrame(data)print(df)# DataFrame转字典列表dict_list = df.to_dict('records')print(dict_list)# DataFrame转JSONjson_data = df.to_json(orient='records')print(json_data)

pythonimport struct# 将整数打包为二进制数据packed_data = struct.pack('iif', 1, 2, 3.14)print(packed_data)  # 输出: b'\x01\x00\x00\x00\x02\x00\x00\x00@\t\x1e\xb8'# 解包二进制数据为整数unpacked_data = struct.unpack('iif', packed_data)print(unpacked_data)  # 输出: (1, 2, 3.140000104904175)

pythondef can_convert_to_int(value):try:int(value)return Trueexcept (ValueError, TypeError):return Falseprint(can_convert_to_int("123"))  # Trueprint(can_convert_to_int("abc"))  # Falseprint(can_convert_to_int(None))   # False

pythonfrom collections.abc import Iterabledef convert_mixed_list(mixed_list):result = []for item in mixed_list:if isinstance(item, str):try:# 尝试转换为数字if '.' in item:num = float(item)else:num = int(item)result.append(num)except ValueError:result.append(item)else:result.append(item)return resultmixed = ["1", "2.5", "abc", 3, "4.0"]converted = convert_mixed_list(mixed)print(converted)  # 输出: [1, 2.5, 'abc', 3, 4.0]

pythondef safe_convert(value, converter, default=None):if value is None:return defaulttry:return converter(value)except (ValueError, TypeError):return defaultprint(safe_convert("123", int))          # 123print(safe_convert("abc", int))          # Noneprint(safe_convert(None, int, 0))        # 0print(safe_convert("3.14", float, 0.0))  # 3.14