Python python39

Author: alisx

taiyangxue/README.md

@@ -13,6 +13,7 @@
 - [sandman2](https://github.com/JustDoPython/python-examples/tree/master/taiyangxue/sandman2) : 不用一行代码，用 API 操作数据库，你信吗
 - [showdata](https://github.com/JustDoPython/python-examples/tree/master/taiyangxue/showdata) : Flask + echarts 轻松搞定 nginx 日志可视化
 - [dice](https://github.com/JustDoPython/python-examples/tree/master/taiyangxue/dice) : 做硬核老爸，我用 Python
+- [python39](https://github.com/JustDoPython/python-examples/tree/master/taiyangxue/python39) : 你在享受十一长假时，Python 已悄悄地变了
 
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taiyangxue/python39/app.py

@@ -0,0 +1,69 @@
+## 字典合并
+d1 = {'a': 'A', 'b': 'B', 'c': 'C'}
+d2 = {'d': 'D', 'e': 'E'}
+
+# 旧版
+d3 = {**d1, **d2}  # 使用展开操作符，将合并结果存入 d3
+print(d3)  # {'a': 'A', 'b': 'B', 'c': 'C', 'd': 'D', 'e': 'E'}
+
+d1.update(d2)  # update 方法，将 d1 d2 合并，且更新 d1
+print(d1)  # {'a': 'A', 'b': 'B', 'c': 'C', 'd': 'D', 'e': 'E'}
+
+# 新版
+d3 = d1 | d2  # 效果等同于展开操作符
+print(d3)  # {'a': 'A', 'b': 'B', 'c': 'C', 'd': 'D', 'e': 'E'}
+
+d1 |= d2  # 等同于 update
+print(d1)  # {'a': 'A', 'b': 'B', 'c': 'C', 'd': 'D', 'e': 'E'}
+
+
+## 拓扑排序
+from graphlib import TopologicalSorter
+
+tg = {5: {3, 4}, 4: {2, 3}, 3: {2, 1}, 2: {1}}
+ts = TopologicalSorter(tg)
+
+print(list(ts.static_order())) # [1, 2, 3, 4, 5]
+
+ts = TopologicalSorter()
+ts.add(5, 3, 4)
+ts.add(4, 2, 3)
+ts.add(3, 2, 1)
+ts.add(2, 1)
+
+print(list(ts.static_order())) # [1, 2, 3, 4, 5]
+
+
+## 随机字节码
+import random
+print(random.randbytes(10))  # b'\x0fzf\x17K\x00\xfb\x11LF'  随机的，每次结果可能不同
+
+
+## 最小公倍数
+import math
+math.lcm(49, 14)  # 98
+
+def lcm(num1, num2):
+  if num1 == num2 == 0:
+    return 0
+  return num1 * num2 // math.gcd(num1, num2)
+
+lcm(49, 14)  # 98
+
+
+## 字符串去前后缀
+"three cool features in Python".removesuffix(" Python")
+# three cool features in
+
+"three cool features in Python".removeprefix("three ")
+# cool features in Python
+
+"three cool features in Python".removeprefix("Something else")
+# three cool features in Python
+
+
+## 时区
+from zoneinfo import ZoneInfo
+from datetime import datetime
+
+dt = datetime(2020, 10, 1, 1, tzinfo= ZoneInfo("America/Los_Angeles"))