print(len(int("")))       # ValueError: invalid literal for int() with base 10: ''
print(len(float("   ")))  # ValueError: could not convert string to float: '   '

invisible_str = "123\u200b"  # 末尾有零寬空格
try:
    int(invisible_str)
except ValueError:
    print("零寬空格導(dǎo)致轉(zhuǎn)換失敗！")

def safe_int(s):
    s_clean = s.strip()
    if not s_clean:
        return None  # 或拋出自定義異常
    try:
        return int(s_clean)
    except ValueError:
        return None

print(safe_int("  123  "))  # 123
print(safe_int(" "))         # None
print(safe_int("\u200b123")) # 123 (strip()移除了零寬空格)

a = float("0.1")
b = float("0.2")
print(a + b == 0.3)  # False!
print(a + b)         # 0.30000000000000004

from decimal import Decimal

a = Decimal("0.1")
b = Decimal("0.2")
print(a + b == Decimal("0.3"))  # True
print(a + b)                   # 0.3

try:
    float("1.000,50")  # 歐式格式（逗號(hào)為小數(shù)點(diǎn)）
except ValueError as e:
    print(f"錯(cuò)誤: {e}")  # 錯(cuò)誤: could not convert string to float: '1.000,50'"

import locale

# 設(shè)置為德語(yǔ)區(qū)域（使用逗號(hào)為小數(shù)點(diǎn)）
locale.setlocale(locale.LC_ALL, 'de_DE.UTF-8')  # 可能需要系統(tǒng)支持
try:
    num = locale.atof("1.000,50")
    print(num)  # 1000.5
except locale.Error:
    print("區(qū)域設(shè)置不可用，請(qǐng)安裝對(duì)應(yīng)locale")

def parse_european_float(s):
    s = s.replace(".", "").replace(",", ".")
    return float(s)

print(parse_european_float("1.000,50"))  # 1000.5

# float的最大值
print(float("1e308"))  # 1e+308
print(float("1e309"))  # inf (溢出為無(wú)窮大)

# int無(wú)上限，但轉(zhuǎn)換極大字符串可能耗盡內(nèi)存
huge_str = "9" * 1000000  # 一百萬(wàn)個(gè)9
try:
    int(huge_str)  # 可能導(dǎo)致MemoryError
except MemoryError:
    print("內(nèi)存不足！")

def safe_float(s):
    try:
        val = float(s)
        if val == float('inf') or val != val:  # 檢查inf和nan
            return None
        return val
    except ValueError:
        return None

def safe_to_int(s, default=None, strip=True, clean_commas=False):
    """
    安全地將字符串轉(zhuǎn)換為整數(shù)
    :param s: 輸入字符串
    :param default: 轉(zhuǎn)換失敗時(shí)的默認(rèn)值
    :param strip: 是否移除前后空白
    :param clean_commas: 是否移除逗號(hào)（用于千位分隔符）
    :return: 整數(shù)或默認(rèn)值
    """
    if strip:
        s = s.strip()
    if not s:
        return default
    
    # 清理逗號(hào)（如"1,000" → "1000"）
    if clean_commas:
        s = s.replace(",", "")
    
    try:
        return int(s)
    except ValueError:
        # 嘗試處理帶小數(shù)點(diǎn)的字符串（如"42.0"）
        try:
            return int(float(s))
        except (ValueError, TypeError):
            return default

# 測(cè)試案例
print(safe_to_int(" 1,234 ", clean_commas=True))  # 1234
print(safe_to_int("42.0", clean_commas=True))     # 42
print(safe_to_int("error", default=0))            # 0

class StringConversionError(ValueError):
    def __init__(self, original_string, message):
        super().__init__(f"轉(zhuǎn)換失敗: '{original_string}' → {message}")
        self.original_string = original_string

def strict_int(s):
    try:
        return int(s)
    except ValueError as e:
        raise StringConversionError(s, str(e)) from None

try:
    strict_int("100元")
except StringConversionError as e:
    print(f"嚴(yán)重錯(cuò)誤: {e}")  # 嚴(yán)重錯(cuò)誤: 轉(zhuǎn)換失敗: '100元' → invalid literal for int() with base 10: '100元'

# ?? 絕對(duì)不要這樣做！
user_input = "__import__('os').system('rm -rf /')"
eval(user_input)  # 可能刪除整個(gè)系統(tǒng)！

import ast

print(ast.literal_eval("3.14"))  # 3.14 (float)
print(ast.literal_eval("[1, 2, 3]"))  # [1, 2, 3] (list)
print(ast.literal_eval("{'a': 1}"))  # {'a': 1} (dict)

# 但數(shù)字字符串仍需額外處理
try:
    ast.literal_eval("100美元")
except ValueError as e:
    print(f"錯(cuò)誤: {e}")  # 錯(cuò)誤: malformed node or string: <ast.Name object at ...>

import re

def is_valid_float(s):
    # 匹配可選符號(hào)、數(shù)字、小數(shù)點(diǎn)、指數(shù)部分
    pattern = r'^[+-]?(\d+(\.\d*)?|\.\d+)([eE][+-]?\d+)?$'
    return bool(re.match(pattern, s.strip()))

print(is_valid_float(" -123.45e-6 "))  # True
print(is_valid_float("1,000"))         # False
print(is_valid_float("NaN"))           # False (需額外處理)

# 使用示例
s = " 3.14 "
if is_valid_float(s):
    num = float(s)
else:
    num = 0.0  # 安全默認(rèn)值

print(float("1.23E4"))  # 12300.0
print(float("1.23e4"))  # 12300.0

print(float("inf"))  # inf
print(float("-inf")) # -inf
print(float("nan"))  # nan

# 檢查nan：不能用==比較
x = float("nan")
print(x == float("nan"))  # False!
print(math.isnan(x))      # True (需import math)

def safe_float_with_checks(s):
    try:
        val = float(s)
        if math.isinf(val) or math.isnan(val):
            return None
        return val
    except ValueError:
        return None

def parse_temperature(s):
    # 提取數(shù)字部分（允許負(fù)號(hào)和小數(shù)點(diǎn)）
    match = re.search(r'[-+]?\d*\.\d+|\d+', s)
    if match:
        return float(match.group())
    return None

print(parse_temperature("當(dāng)前溫度: -5.2°C"))  # -5.2
print(parse_temperature("無(wú)效輸入"))          # None

cleaned = user_input.strip().replace("$", "").replace(",", "")

int("10", 16)  # 明確十六進(jìn)制

try:
    num = int(s)
except ValueError:
    num = DEFAULT

if abs(a - b) < 1e-9:  # 容差比較
    print("相等")

from decimal import Decimal
total = Decimal("0.1") + Decimal("0.2")  # 精確為0.3

if not re.fullmatch(r'-?\d+', s):
    raise ValueError("非整數(shù)字符串")

logger.error(f"轉(zhuǎn)換失敗: '{raw_input}' 在行 {line_num}")

# ?? 危險(xiǎn)示例！
s = input("輸入數(shù)字: ")
num = eval(s)  # 如果輸入"__import__('os').system('rm -rf /')", 你的系統(tǒng)完蛋了

import timeit

# 方法1: 直接轉(zhuǎn)換
def direct():
    return int("12345")

# 方法2: 帶try-except
def safe():
    try:
        return int("12345")
    except ValueError:
        return 0

# 方法3: 正則預(yù)驗(yàn)證
def regex():
    if re.match(r'^-?\d+$', "12345"):
        return int("12345")
    return 0

print(timeit.timeit(direct, number=1000000))  # ~0.1秒
print(timeit.timeit(safe, number=1000000))    # ~0.15秒 (異常成本高)
print(timeit.timeit(regex, number=1000000))   # ~0.3秒 (正則較慢)

# 錯(cuò)誤：未指定單位
altitude_ft = float(sensor_data)  # 但傳感器輸出的是米？

price = float(user_input)  # "1.000" → 1.0 (而非1000.0)

# 根據(jù)用戶區(qū)域設(shè)置解析
if user_locale == "de_DE":
    price = float(user_input.replace(".", "").replace(",", "."))
else:
    price = float(user_input.replace(",", ""))

import math
print(math.isclose(0.1 + 0.2, 0.3))  # True