阅读python文档

python/py.md

@@ -482,3 +482,215 @@ def fuck(*name_list):
 
 fuck("Nvidia", "Amd")
 ```
+## 文件操作
+### 文件读取
+```py
+with open('pi_digits.txt') as file_object:
+    contents = file_object.read()
+    print(contents)
+```
+### 写入文件
+```py
+filename = 'programming.txt'
+with open(filename, 'w') as file_object:
+    file_object.write("I love programming.")
+    file_object.write("I love creating new games.")
+```
+
+### 文件末尾追加
+```py
+filename = 'programming.txt'
+with open(filename, 'a') as file_object:
+    file_object.write("I also love finding meaning in large datasets.\n")
+    file_object.write("I love creating apps that can run in a browser.\n")
+```
+## 异常处理
+在python中，可以通过如下语法来进行异常处理
+```py
+try:
+    # code block
+    pass
+except ErrorType1:
+    # error type 1 handling code block
+    pass
+except ErrorType2:
+    # error type 2 handling code block
+    pass
+except Exception as result:
+    # handle other exception types
+    pass
+else:
+    # code block that no error occurs
+    pass
+finally:
+    # code block executed whether exception occurs
+    pass
+```
+
+### 抛异常
+#### 捕获异常后重新抛出异常
+如果python在捕获异常后需要重新对异常进行抛出，可以使用`raise`关键字
+```py
+try:
+    m = 10/0
+except Exception as e:
+    print(e)
+    raise
+finally:
+    print("handle correctly")
+```
+#### 主动抛出异常
+主动抛出异常时，也可使用`raise`关键字
+```py
+try:
+    raise Exception("fucking Nvidia raised their price!")
+except Exception as e:
+    print(e)
+finally:
+    print("my wallet is empty!")
+```
+
+## 数据存储
+### json.dump
+可以通过`json.dump`方法将内容以json的格式存储到文件中：
+```py
+import json
+
+
+def save_as_json(data, fd):
+    json.dump(data, fd)
+
+
+waifu = {
+    "name": "Touma Kazusa",
+    "job": "Student",
+    "gender": "female",
+    "age": 17
+}
+
+is_save_success = True
+try:
+    with open("shiro.json", "w") as shiro_fd:
+        save_as_json(waifu, shiro_fd)
+except Exception as e:
+    print(e)
+    is_save_success = False
+    exit(1)
+finally:
+    if is_save_success:
+        print("save success!")
+```
+### json.load
+可以通过`json.load`方法读取文件中的json格式内容：
+```py
+import json
+
+
+def read_as_json(fd):
+    return json.load(fd)
+
+
+is_read_success = True
+try:
+    with open("shiro.json", "r") as shiro_fd:
+        r_obj = read_as_json(shiro_fd)
+        print(r_obj)
+except Exception as e:
+    print(e)
+    is_read_success = False
+    exit(1)
+finally:
+    if is_read_success:
+        print("read success!")
+```
+## http api
+python安装requests包之后，可以访问http接口
+```py
+import math
+import requests
+import time
+
+try:
+    body = requests.get("https://api.m.taobao.com/rest/api3.do", {
+        "api": "mtop.common.getTimestamp"
+    }).json()
+    ts = body['data']['t']
+    t = time.localtime(math.trunc(int(ts) / 1000))
+    time_str = time.strftime("%Y-%m-%d %H:%M:%S %z", t)
+    print(time_str)
+except Exception as e:
+    print(e)
+    raise
+```
+
+## 多线程
+python可以通过引入threading和concurrent.futures两个包来引入多线程：
+```py
+import math
+import time
+from concurrent.futures import ThreadPoolExecutor, as_completed
+import threading
+
+import requests
+
+ts_arr = []
+lock = threading.Lock()
+
+
+def query_ts():
+    try:
+        body = requests.get("https://api.m.taobao.com/rest/api3.do", {
+            "api": "mtop.common.getTimestamp"
+        }).json()
+    except Exception as e:
+        print(e)
+        raise
+
+
+def query_ts_once():
+    ts_beg = time.time_ns()
+    query_ts()
+    ts_end = time.time_ns()
+    ts_spend = math.trunc((ts_end - ts_beg) / 1000000)
+    with lock:
+        ts_arr.append(ts_spend)
+
+
+def stress_test(test_cnt):
+    with ThreadPoolExecutor(max_workers=32) as executor:
+        i = 0
+        f_list = []
+        while i < test_cnt:
+            f_t = executor.submit(query_ts_once)
+            f_list.append(f_t)
+            i += 1
+        as_completed(f_list)
+
+
+stress_test(100)
+print(f"max ts : {max(ts_arr)} ms")
+print(f"min ts : {min(ts_arr)} ms")
+print(f"avg ts : {sum(ts_arr) / len(ts_arr)} ms")
+print(ts_arr)
+```
+
+## linux命令交互
+如果想要调用系统（linux）的命令，可以使用subprocess模块。
+```py
+subprocess.run(args, *, stdin=None, input=None, stdout=None, stderr=None, capture_output=False, shell=False, cwd=None, timeout=None, check=False, encoding=None, errors=None, text=None, env=None, universal_newlines=None)
+```
+调用示例如下：
+```py
+ret = subprocess.run(['ls', '-l'], capture_output=True, text=True)
+print(ret.stdout)
+```
+输出如下：
+```bash
+total 4
+-rwxrwxrwx 1 asahi asahi  110 May  4 03:18 main.py
+-rwxrwxrwx 1 asahi asahi   73 May  4 01:10 shiro.json
+drwxrwxrwx 1 asahi asahi 4096 Feb  7 21:39 venv
+```
+
+
+