完成 q4_3 评分+时长直方图

q4/q4_3a/q4_3a.py

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+# q4_3a.py
+import json
+import matplotlib.pyplot as plt
+
+# 读取数据
+with open("movies.json", "r", encoding="utf-8") as f:
+    data = json.load(f)
+
+movies = data["movies"]
+
+# 提取评分
+ratings = []
+for m in movies:
+    ratings.append(m["rating"])
+
+# 绘制直方图
+plt.hist(ratings, bins=5, color="blue")
+plt.title("评分分布")
+plt.xlabel("评分")
+
+# 保存图片
+plt.savefig("q4_3a_hist.png", dpi=150)
+plt.close()
+
+print("✅ q4_3a 完成！")