rosermf2040 · rosermf2040 · Mar 17, 2026 · Mar 27, 2026
diff --git a/README.md b/README.md
@@ -1,4 +1,28 @@
-abc
-===
+# abc
 
-we start it now
+一个使用 Python（Flask）实现的简单网页计算器。
+
+## 功能
+- 网页输入算术表达式并计算结果
+- 支持 `+ - * / % **` 与括号
+- 对非法输入给出错误提示
+
+## 运行方式
+```bash
+python3 -m venv .venv
+source .venv/bin/activate
+pip install -r requirements.txt
+python app.py
+```
+
+## 直接运行核心程序
+```bash
+python calculator_core.py "1 + 2 * (3 - 1)"
+```
+
+## 测试
+```bash
+python -m unittest discover -s tests
+```
+
+浏览器访问：`http://127.0.0.1:5000`
diff --git a/app.py b/app.py
@@ -0,0 +1,25 @@
+from flask import Flask, render_template, request
+
+from calculator_core import evaluate_expression
+
+app = Flask(__name__)
+
+
+@app.route("/", methods=["GET", "POST"])
+def calculator():
+    expression = ""
+    result = None
+    error = None
+
+    if request.method == "POST":
+        expression = request.form.get("expression", "")
+        try:
+            result = evaluate_expression(expression)
+        except Exception as exc:
+            error = str(exc)
+
+    return render_template("calculator.html", expression=expression, result=result, error=error)
+
+
+if __name__ == "__main__":
+    app.run(host="0.0.0.0", port=5000, debug=True)
diff --git a/calculator_core.py b/calculator_core.py
@@ -0,0 +1,88 @@
+from __future__ import annotations
+
+import argparse
+import ast
+import sys
+
+
+class SafeEvaluator(ast.NodeVisitor):
+    """Safely evaluate arithmetic expressions."""
+
+    ALLOWED_BINOPS = (ast.Add, ast.Sub, ast.Mult, ast.Div, ast.Pow, ast.Mod)
+    ALLOWED_UNARYOPS = (ast.UAdd, ast.USub)
+
+    def visit_Expression(self, node: ast.Expression) -> float:
+        return self.visit(node.body)
+
+    def visit_BinOp(self, node: ast.BinOp) -> float:
+        if not isinstance(node.op, self.ALLOWED_BINOPS):
+            raise ValueError("不支持的运算符")
+        left = self.visit(node.left)
+        right = self.visit(node.right)
+
+        if isinstance(node.op, ast.Add):
+            return left + right
+        if isinstance(node.op, ast.Sub):
+            return left - right
+        if isinstance(node.op, ast.Mult):
+            return left * right
+        if isinstance(node.op, ast.Div):
+            if right == 0:
+                raise ValueError("除数不能为 0")
+            return left / right
+        if isinstance(node.op, ast.Pow):
+            return left**right
+        if isinstance(node.op, ast.Mod):
+            return left % right
+
+        raise ValueError("不支持的运算")
+
+    def visit_UnaryOp(self, node: ast.UnaryOp) -> float:
+        if not isinstance(node.op, self.ALLOWED_UNARYOPS):
+            raise ValueError("不支持的一元运算符")
+        value = self.visit(node.operand)
+        return +value if isinstance(node.op, ast.UAdd) else -value
+
+    def visit_Constant(self, node: ast.Constant) -> float:
+        value = node.value
+        if isinstance(value, bool) or not isinstance(value, (int, float)):
+            raise ValueError("只允许数字")
+        return float(value)
+
+    def visit_Num(self, node: ast.Num) -> float:  # pragma: no cover (compat)
+        return float(node.n)
+
+    def generic_visit(self, node: ast.AST):
+        raise ValueError("表达式包含不允许的内容")
+
+
+def evaluate_expression(expression: str) -> float:
+    if not expression.strip():
+        raise ValueError("请输入表达式")
+
+    parsed = ast.parse(expression, mode="eval")
+    evaluator = SafeEvaluator()
+    return evaluator.visit(parsed)
+
+
+def main(argv: list[str] | None = None) -> int:
+    parser = argparse.ArgumentParser(description="Safely evaluate arithmetic expressions.")
+    parser.add_argument("expression", nargs="?", help="要计算的算术表达式")
+    args = parser.parse_args(argv)
+
+    if not args.expression:
+        parser.print_help()
+        return 0
+
+    try:
+        result = evaluate_expression(args.expression)
+    except Exception as exc:
+        print(f"错误：{exc}", file=sys.stderr)
+        return 1
+
+    print(result)
+    return 0
+
+
+if __name__ == "__main__":
+    raise SystemExit(main())
diff --git a/requirements.txt b/requirements.txt
@@ -0,0 +1 @@
+Flask==3.0.3
diff --git a/templates/calculator.html b/templates/calculator.html
@@ -0,0 +1,68 @@
+<!DOCTYPE html>
+<html lang="zh-CN">
+<head>
+    <meta charset="UTF-8" />
+    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
+    <title>Python 网页计算器</title>
+    <style>
+        :root { font-family: Arial, sans-serif; }
+        body {
+            margin: 0;
+            min-height: 100vh;
+            display: grid;
+            place-items: center;
+            background: linear-gradient(135deg, #dbeafe, #f5f3ff);
+        }
+        .card {
+            width: min(92vw, 460px);
+            background: white;
+            border-radius: 16px;
+            box-shadow: 0 12px 32px rgba(0,0,0,.12);
+            padding: 24px;
+        }
+        h1 { margin-top: 0; font-size: 1.4rem; }
+        p.hint { color: #4b5563; margin-top: 4px; }
+        input[type="text"] {
+            width: 100%;
+            font-size: 1.1rem;
+            padding: 12px;
+            border: 1px solid #d1d5db;
+            border-radius: 10px;
+            box-sizing: border-box;
+        }
+        button {
+            margin-top: 12px;
+            width: 100%;
+            background: #2563eb;
+            color: white;
+            border: none;
+            padding: 12px;
+            font-size: 1rem;
+            border-radius: 10px;
+            cursor: pointer;
+        }
+        .result { margin-top: 14px; font-weight: bold; color: #047857; }
+        .error { margin-top: 14px; font-weight: bold; color: #b91c1c; }
+    </style>
+</head>
+<body>
+    <div class="card">
+        <h1>Python 网页计算器</h1>
+        <p class="hint">支持 + - * / % ** 和括号，如： (2+3)*4 / 5</p>
+
+        <form method="post">
+            <label for="expression">请输入表达式：</label>
+            <input id="expression" type="text" name="expression" value="{{ expression }}" placeholder="例如：1 + 2 * (3 - 1)" required>
+            <button type="submit">计算</button>
+        </form>
+
+        {% if result is not none %}
+        <div class="result">结果：{{ result }}</div>
+        {% endif %}
+
+        {% if error %}
+        <div class="error">错误：{{ error }}</div>
+        {% endif %}
+    </div>
+</body>
+</html>
diff --git a/tests/test_calculator_core.py b/tests/test_calculator_core.py
@@ -0,0 +1,29 @@
+import io
+import unittest
+from contextlib import redirect_stdout
+
+from calculator_core import evaluate_expression, main
+
+
+class CalculatorCoreTests(unittest.TestCase):
+    def test_evaluate_expression_basic_math(self):
+        self.assertEqual(evaluate_expression("1 + 2 * (3 - 1)"), 5.0)
+
+    def test_evaluate_expression_rejects_bool_constants(self):
+        with self.assertRaisesRegex(ValueError, "只允许数字"):
+            evaluate_expression("True")
+
+    def test_evaluate_expression_rejects_division_by_zero(self):
+        with self.assertRaisesRegex(ValueError, "除数不能为 0"):
+            evaluate_expression("1 / 0")
+
+    def test_main_prints_result_for_cli_argument(self):
+        buffer = io.StringIO()
+        with redirect_stdout(buffer):
+            code = main(["2 + 3"])
+        self.assertEqual(code, 0)
+        self.assertEqual(buffer.getvalue().strip(), "5.0")
+
+
+if __name__ == "__main__":
+    unittest.main()