{"id":43501,"date":"2025-07-31T21:28:03","date_gmt":"2025-07-31T12:28:03","guid":{"rendered":"https:\/\/techgym.jp\/?p=43501"},"modified":"2025-07-31T21:31:19","modified_gmt":"2025-07-31T12:31:19","slug":"float","status":"publish","type":"post","link":"https:\/\/techgym.jp\/column\/float\/","title":{"rendered":"Python\u306efloat()\u95a2\u6570\u3092\u5fb9\u5e95\u89e3\u8aac\uff01\u6d6e\u52d5\u5c0f\u6570\u70b9\u6570\u3078\u306e\u5909\u63db\u304b\u3089\u6ce8\u610f\u70b9\u307e\u3067"},"content":{"rendered":"\n

\n

\u00a0<\/p>\n

Python\u3067\u6570\u5024\u8a08\u7b97\u3092\u884c\u3046\u969b\u3001\u6574\u6570\u3060\u3051\u3067\u306a\u304f\u5c0f\u6570\uff08\u6d6e\u52d5\u5c0f\u6570\u70b9\u6570\uff09\u3092\u6271\u3046\u6a5f\u4f1a\u306f\u975e\u5e38\u306b\u591a\u3044\u3067\u3059\u3002\u7279\u306b\u3001\u6587\u5b57\u5217\u3067\u8868\u73fe\u3055\u308c\u305f\u6570\u5024\u3092\u8a08\u7b97\u306b\u4f7f\u3044\u305f\u3044\u5834\u5408\u3084\u3001\u6574\u6570\u3092\u5c0f\u6570\u3068\u3057\u3066\u6271\u3044\u305f\u3044\u5834\u5408\u306b\u6d3b\u8e8d\u3059\u308b\u306e\u304cfloat()<\/code>\u95a2\u6570<\/b>\u3067\u3059\u3002\u3053\u306e\u8a18\u4e8b\u3067\u306f\u3001Python\u306efloat()<\/code>\u95a2\u6570\u306e\u57fa\u672c\u7684\u306a\u4f7f\u3044\u65b9\u304b\u3089\u3001\u77e5\u3063\u3066\u304a\u304f\u3079\u304d\u6ce8\u610f\u70b9\u3001\u3055\u3089\u306b\u306f\u6d3b\u7528\u4e8b\u4f8b\u307e\u3067\u3092\u521d\u5fc3\u8005\u306b\u3082\u308f\u304b\u308a\u3084\u3059\u304f\u89e3\u8aac\u3057\u307e\u3059\u3002<\/p>\n

\u00a0<\/p>\n

float()<\/code>\u95a2\u6570\u3068\u306f\uff1fPython\u306b\u304a\u3051\u308b\u6d6e\u52d5\u5c0f\u6570\u70b9\u6570\u3078\u306e\u578b\u5909\u63db<\/h2>\n

\u00a0<\/p>\n

Python\u306efloat()<\/code>\u95a2\u6570\u306f\u3001\u5f15\u6570\u3068\u3057\u3066\u6e21\u3055\u308c\u305f\u5024\u3092\u6d6e\u52d5\u5c0f\u6570\u70b9\u6570\uff08floating-point number\uff09\u306b\u5909\u63db<\/b>\u3059\u308b\u305f\u3081\u306e\u7d44\u307f\u8fbc\u307f\u95a2\u6570\u3067\u3059\u3002\u7570\u306a\u308b\u30c7\u30fc\u30bf\u578b\u306e\u5024\u3092\u5c0f\u6570\u3068\u3057\u3066\u6271\u3044\u305f\u3044\u5834\u5408\u306b\u975e\u5e38\u306b\u5f79\u7acb\u3061\u307e\u3059\u3002<\/p>\n

\u00a0<\/p>\n

\u57fa\u672c\u7684\u306a\u4f7f\u3044\u65b9\uff1a\u6587\u5b57\u5217\u304b\u3089\u306e\u5909\u63db<\/h3>\n

\u00a0<\/p>\n

\u6700\u3082\u3088\u304f\u4f7f\u308f\u308c\u308b\u306e\u306f\u3001\u6570\u5b57\u3067\u69cb\u6210\u3055\u308c\u305f\u6587\u5b57\u5217\u3092\u6d6e\u52d5\u5c0f\u6570\u70b9\u6570\u306b\u5909\u63db\u3059\u308b\u30b1\u30fc\u30b9\u3067\u3059\u3002\u3053\u308c\u306f\u3001\u30e6\u30fc\u30b6\u30fc\u304b\u3089\u306e\u5165\u529b\u304c\u6587\u5b57\u5217\u3068\u3057\u3066\u53d7\u3051\u53d6\u3089\u308c\u308b\u5834\u5408\u306a\u3069\u306b\u975e\u5e38\u306b\u4fbf\u5229\u3067\u3059\u3002<\/p>\n

\n
Python<\/span>\n
\u00a0<\/div>\n<\/div>\n
\n
\n
# \u6587\u5b57\u5217\u3092\u6d6e\u52d5\u5c0f\u6570\u70b9\u6570\u306b\u5909\u63db\u3059\u308b\u4f8b<\/span>\nstr_num = \"3.14\"<\/span>\nfloat_num = float<\/span>(str_num)\nprint(float_num) # \u51fa\u529b: 3.14<\/span>\nprint(type<\/span>(float_num)) # \u51fa\u529b: <class 'float'><\/span>\n\n# \u6574\u6570\u3092\u8868\u3059\u6587\u5b57\u5217\u3082\u5909\u63db\u53ef\u80fd<\/span>\nstr_int = \"100\"<\/span>\nfloat_from_int_str = float<\/span>(str_int)\nprint(float_from_int_str) # \u51fa\u529b: 100.0<\/span>\n<\/code><\/pre>\n<\/div>\n<\/div>\n<\/div>\n
\u6ce8\u610f\u70b9:<\/b> \u6570\u5b57\u3084\u5c0f\u6570\u70b9\u3001\u7b26\u53f7\uff08+,-\uff09\u4ee5\u5916\u306e\u6587\u5b57\u304c\u542b\u307e\u308c\u3066\u3044\u308b\u6587\u5b57\u5217\u3092float()<\/code>\u95a2\u6570\u3067\u5909\u63db\u3057\u3088\u3046\u3068\u3059\u308b\u3068\u3001ValueError<\/code>\u304c\u767a\u751f\u3057\u307e\u3059\u3002<\/p>\n
\n
Python<\/span>\n
\u00a0<\/div>\n<\/div>\n
\n
\n
# \u30a8\u30e9\u30fc\u306b\u306a\u308b\u4f8b<\/span>\n# invalid_str = \"3.14abc\"<\/span>\n# invalid_float = float(invalid_str) # ValueError: could not convert string to float: '3.14abc'<\/span>\n\n# invalid_str2 = \"\u5186\u5468\u73873.14\"<\/span>\n# invalid_float2 = float(invalid_str2) # ValueError: could not convert string to float: '\u5186\u5468\u73873.14'<\/span>\n<\/code><\/pre>\n<\/div>\n<\/div>\n<\/div>\n
\u00a0<\/p>\n
\u6574\u6570\u304b\u3089\u306e\u5909\u63db<\/h3>\n
\u00a0<\/p>\n
float()<\/code>\u95a2\u6570\u306f\u3001\u6574\u6570\u3092\u6d6e\u52d5\u5c0f\u6570\u70b9\u6570\u306b\u5909\u63db\u3059\u308b\u3053\u3068\u3082\u3067\u304d\u307e\u3059\u3002\u3053\u306e\u5834\u5408\u3001.0<\/code>\u304c\u8ffd\u52a0\u3055\u308c\u307e\u3059\u3002<\/p>\n
\n
Python<\/span>\n
\u00a0<\/div>\n<\/div>\n
\n
\n
# \u6574\u6570\u3092\u6d6e\u52d5\u5c0f\u6570\u70b9\u6570\u306b\u5909\u63db\u3059\u308b\u4f8b<\/span>\ninteger_val = 5<\/span>\nfloat_from_int = float<\/span>(integer_val)\nprint(float_from_int) # \u51fa\u529b: 5.0<\/span>\nprint(type<\/span>(float_from_int)) # \u51fa\u529b: <class 'float'><\/span>\n<\/code><\/pre>\n<\/div>\n<\/div>\n<\/div>\n
\u00a0<\/p>\n
\u4ed6\u306e\u578b\u304b\u3089\u306e\u5909\u63db<\/h3>\n
\u00a0<\/p>\n
\u30d6\u30fc\u30eb\u5024\uff08True<\/code>\/False<\/code>\uff09\u3092\u5909\u63db\u3059\u308b\u3053\u3068\u3082\u53ef\u80fd\u3067\u3059\u3002True<\/code>\u306f1.0<\/code>\u306b\u3001False<\/code>\u306f0.0<\/code>\u306b\u5909\u63db\u3055\u308c\u307e\u3059\u3002<\/p>\n
\n
Python<\/span>\n
\u00a0<\/div>\n<\/div>\n
\n
\n
print(float<\/span>(True<\/span>))  # \u51fa\u529b: 1.0<\/span>\nprint(float<\/span>(False<\/span>)) # \u51fa\u529b: 0.0<\/span>\n<\/code><\/pre>\n<\/div>\n<\/div>\n<\/div>\n
\u00a0<\/p>\n
float()<\/code>\u95a2\u6570\u306e\u6ce8\u610f\u70b9\u3068\u6d3b\u7528\u4e8b\u4f8b<\/h2>\n
\u00a0<\/p>\n
\u00a0<\/p>\n
1. \u6d6e\u52d5\u5c0f\u6570\u70b9\u6570\u8a08\u7b97\u306e\u7cbe\u5ea6\u554f\u984c<\/h3>\n
\u00a0<\/p>\n
\u30b3\u30f3\u30d4\u30e5\u30fc\u30bf\u306f\u6d6e\u52d5\u5c0f\u6570\u70b9\u6570\u3092\u53b3\u5bc6\u306b\u8868\u73fe\u3067\u304d\u306a\u3044\u5834\u5408\u304c\u3042\u308b\u305f\u3081\u3001\u8a08\u7b97\u7d50\u679c\u306b\u308f\u305a\u304b\u306a\u8aa4\u5dee\u304c\u751f\u3058\u308b\u3053\u3068\u304c\u3042\u308a\u307e\u3059\u3002\u3053\u308c\u306ffloat()<\/code>\u95a2\u6570\u81ea\u4f53\u306e\u554f\u984c\u3067\u306f\u3042\u308a\u307e\u305b\u3093\u304c\u3001\u6d6e\u52d5\u5c0f\u6570\u70b9\u6570\u3092\u6271\u3046\u4e0a\u3067\u5e38\u306b\u610f\u8b58\u3059\u3079\u304d\u70b9\u3067\u3059\u3002<\/p>\n
\n
Python<\/span>\n
\u00a0<\/div>\n<\/div>\n
\n
\n
# \u6d6e\u52d5\u5c0f\u6570\u70b9\u6570\u306e\u7cbe\u5ea6\u554f\u984c\u306e\u4f8b<\/span>\n# 0.1\u309210\u56de\u8db3\u3057\u3066\u3082\u3001\u53b3\u5bc6\u306b1.0\u306b\u306f\u306a\u3089\u306a\u3044\u53ef\u80fd\u6027\u304c\u3042\u308b<\/span>\nsum_val = 0.0<\/span>\nfor<\/span> _ in<\/span> range<\/span>(10<\/span>):\n    sum_val += 0.1<\/span>\nprint(sum_val) # \u51fa\u529b\u4f8b: 0.9999999999999999 (\u74b0\u5883\u306b\u3088\u308a\u7570\u306a\u308b)<\/span>\n\n# \u53b3\u5bc6\u306a\u8a08\u7b97\u304c\u5fc5\u8981\u306a\u5834\u5408\u306fdecimal\u30e2\u30b8\u30e5\u30fc\u30eb\u3092\u691c\u8a0e<\/span>\nfrom<\/span> decimal import<\/span> Decimal\nprint(Decimal('0.1'<\/span>) * 10<\/span>) # \u51fa\u529b: 1.0<\/span>\n<\/code><\/pre>\n<\/div>\n<\/div>\n<\/div>\n
\u00a0<\/p>\n
2. \u30e6\u30fc\u30b6\u30fc\u5165\u529b\u306e\u6570\u5024\u51e6\u7406<\/h3>\n
\u00a0<\/p>\n
\u30a6\u30a7\u30d6\u30d5\u30a9\u30fc\u30e0\u3084\u30b3\u30de\u30f3\u30c9\u30e9\u30a4\u30f3\u5f15\u6570\u306a\u3069\u3001\u30e6\u30fc\u30b6\u30fc\u304b\u3089\u306e\u6570\u5024\u5165\u529b\u306f\u901a\u5e38\u6587\u5b57\u5217\u3068\u3057\u3066\u53d7\u3051\u53d6\u3089\u308c\u307e\u3059\u3002\u8a08\u7b97\u3092\u884c\u3046\u305f\u3081\u306b\u306f\u3001float()<\/code>\u95a2\u6570\u3092\u4f7f\u3063\u3066\u6570\u5024\u578b\u306b\u5909\u63db\u3059\u308b\u5fc5\u8981\u304c\u3042\u308a\u307e\u3059\u3002<\/p>\n
\n
Python<\/span>\n
\u00a0<\/div>\n<\/div>\n
\n
\n
price_str = input<\/span>(\"\u5546\u54c1\u306e\u4fa1\u683c\u3092\u5165\u529b\u3057\u3066\u304f\u3060\u3055\u3044: \"<\/span>) # \u4f8b: \"99.99\"<\/span>\nquantity_str = input<\/span>(\"\u8cfc\u5165\u6570\u3092\u5165\u529b\u3057\u3066\u304f\u3060\u3055\u3044: \"<\/span>) # \u4f8b: \"2\"<\/span>\n\ntry<\/span>:\n    price = float<\/span>(price_str)\n    quantity = int<\/span>(quantity_str) # \u6570\u91cf\u306f\u6574\u6570\u304c\u826f\u3044\u5834\u5408<\/span>\n    total_cost = price * quantity\n    print(f\"\u5408\u8a08\u91d1\u984d: {total_cost:.2<\/span>f}<\/span>\u5186\"<\/span>) # \u5c0f\u6570\u70b9\u4ee5\u4e0b2\u6841\u3067\u8868\u793a<\/span>\nexcept<\/span> ValueError:\n    print(\"\u6709\u52b9\u306a\u6570\u5024\u3092\u5165\u529b\u3057\u3066\u304f\u3060\u3055\u3044\u3002\"<\/span>)\n<\/code><\/pre>\n<\/div>\n<\/div>\n<\/div>\n
\u00a0<\/p>\n
3. \u30c7\u30fc\u30bf\u89e3\u6790\u3068\u79d1\u5b66\u8a08\u7b97<\/h3>\n
\u00a0<\/p>\n
CSV\u30d5\u30a1\u30a4\u30eb\u306a\u3069\u304b\u3089\u8aad\u307f\u8fbc\u3093\u3060\u30c7\u30fc\u30bf\u306f\u3001\u3057\u3070\u3057\u3070\u6587\u5b57\u5217\u3068\u3057\u3066\u6271\u308f\u308c\u307e\u3059\u3002\u6570\u5024\u3068\u3057\u3066\u5206\u6790\u3092\u884c\u3046\u305f\u3081\u306b\u306f\u3001float()<\/code>\u95a2\u6570\u3084Pandas\u30e9\u30a4\u30d6\u30e9\u30ea\u306e\u578b\u5909\u63db\u6a5f\u80fd\u306a\u3069\u3092\u5229\u7528\u3057\u3066\u6570\u5024\u578b\u306b\u5909\u63db\u3059\u308b\u5fc5\u8981\u304c\u3042\u308a\u307e\u3059\u3002<\/p>\n
\n
Python<\/span>\n
\u00a0<\/div>\n<\/div>\n
\n
\n
# \u4f8b: \u30c7\u30fc\u30bf\u30d5\u30ec\u30fc\u30e0\u306e\u4e00\u90e8\u306e\u5217\u3092\u6d6e\u52d5\u5c0f\u6570\u70b9\u6570\u306b\u5909\u63db<\/span>\nimport<\/span> pandas as<\/span> pd\ndata = {'\u5546\u54c1\u540d'<\/span>: ['A'<\/span>, 'B'<\/span>], '\u4fa1\u683c'<\/span>: ['123.50'<\/span>, '45.75'<\/span>]}\ndf = pd.DataFrame(data)\nprint(\"\u5909\u63db\u524d:\\n\"<\/span>, df.dtypes)\n\ndf['\u4fa1\u683c'<\/span>] = df['\u4fa1\u683c'<\/span>].astype(float<\/span>) # Pandas\u3067float\u578b\u306b\u5909\u63db<\/span>\nprint(\"\\n\u5909\u63db\u5f8c:\\n\"<\/span>, df.dtypes)\n<\/code><\/pre>\n<\/div>\n<\/div>\n<\/div>\n
\u00a0<\/p>\n
float()<\/code>\u95a2\u6570\u3068\u3088\u304f\u6bd4\u8f03\u3055\u308c\u308b\u95a2\u6570<\/h2>\n
\u00a0<\/p>\n
\u00a0<\/p>\n
int()<\/code>\u95a2\u6570\u3068\u306e\u9055\u3044<\/h3>\n
\u00a0<\/p>\n
float()<\/code>\u95a2\u6570\u304c\u6d6e\u52d5\u5c0f\u6570\u70b9\u6570\uff08\u5c0f\u6570\uff09\u3078\u5909\u63db\u3059\u308b\u306e\u306b\u5bfe\u3057\u3001int()<\/code>\u95a2\u6570\u306f\u6574\u6570\u3078\u5909\u63db<\/b>\u3057\u307e\u3059\u3002int()<\/code>\u95a2\u6570\u306f\u5c0f\u6570\u70b9\u4ee5\u4e0b\u3092\u5207\u308a\u6368\u3066\u307e\u3059\u3002<\/p>\n
\n
Python<\/span>\n
\u00a0<\/div>\n<\/div>\n
\n
\n
print(float<\/span>(10<\/span>))    # \u51fa\u529b: 10.0<\/span>\nprint(int<\/span>(3.14<\/span>))    # \u51fa\u529b: 3 (\u5207\u308a\u6368\u3066)<\/span>\nprint(float<\/span>(\"3.14\"<\/span>))# \u51fa\u529b: 3.14<\/span>\nprint(int<\/span>(\"3\"<\/span>))     # \u51fa\u529b: 3<\/span>\n<\/code><\/pre>\n<\/div>\n<\/div>\n<\/div>\n
\u00a0<\/p>\n
str()<\/code>\u95a2\u6570\u3068\u306e\u9055\u3044<\/h3>\n
\u00a0<\/p>\n
float()<\/code>\u95a2\u6570\u304c\u4ed6\u306e\u578b\u3092\u6d6e\u52d5\u5c0f\u6570\u70b9\u6570\u306b\u5909\u63db\u3059\u308b\u306e\u306b\u5bfe\u3057\u3001str()<\/code>\u95a2\u6570\u306f\u4ed6\u306e\u578b\u3092\u6587\u5b57\u5217\u306b\u5909\u63db<\/b>\u3057\u307e\u3059\u3002<\/p>\n
\n
Python<\/span>\n
\u00a0<\/div>\n<\/div>\n
\n
\n
num = 123.45<\/span>\nstr_num = str<\/span>(num)\nprint(str_num) # \u51fa\u529b: \"123.45\"<\/span>\nprint(type<\/span>(str_num)) # \u51fa\u529b: <class 'str'><\/span>\n<\/code><\/pre>\n<\/div>\n<\/div>\n<\/div>\n
\u00a0<\/p>\n
\u307e\u3068\u3081<\/h2>\n
\u00a0<\/p>\n
Python\u306efloat()<\/code>\u95a2\u6570\u306f\u3001\u6d6e\u52d5\u5c0f\u6570\u70b9\u6570\u3092\u6271\u3046\u4e0a\u3067\u4e0d\u53ef\u6b20\u306a\u30c4\u30fc\u30eb\u3067\u3059\u3002\u6587\u5b57\u5217\u3084\u6574\u6570\u3092\u5c0f\u6570\u3068\u3057\u3066\u5229\u7528\u53ef\u80fd\u306b\u3059\u308b\u3053\u3068\u3067\u3001\u5e45\u5e83\u3044\u6570\u5024\u8a08\u7b97\u3084\u30c7\u30fc\u30bf\u51e6\u7406\u306e\u57fa\u76e4\u3068\u306a\u308a\u307e\u3059\u3002<\/p>\n