[Python知识库]python 文件异常

文件读写追加:
f = open(‘文件路径\名称\格式’,mode=(r/w/a),encoding = ‘UTF-8’)
file = f.read/write()
print(file)
or
with open(‘文件路径\名称\格式’,‘r/w/a’,encoding = ‘UTF-8’) as f:
file = f.read/write()
print(file)
文件异常:try - except:
try:
检测范围
except Exception(as reason):
出现异常(Exception)后处理的代码
while True:
try:
x = int(input("请输入一个数字: "))
break
except ValueError:
print(“您输入的不是数字，请再次尝试输入！”)
except子句可以同时处理多个异常，这些异常将被放在一个括号里成为一个元组:except (RuntimeError, TypeError, NameError):

  import sys

   

```python
 try:
        f = open('myfile.txt')
        s = f.readline()
        i = int(s.strip())
    except OSError as err:
        print("OS error: {0}".format(err))
    except ValueError:
        print("Could not convert data to an integer.")
    except:
        print("Unexpected error:", sys.exc_info()[0])
        raise

   

```python
 try:
        f = open('stu.txt','r',encoding='utf-8')
        print(f.read())
        f.close()
        
    except OSError:
        print('文件错了!')
    try/except...else:
    import sys
    for arg in sys.argv[1:]:
        try:
            f = open(arg, 'r')
        except IOError:
            print('cannot open', arg)
        else:
            print(arg, 'has', len(f.readlines()), 'lines')
            f.close()

try - finally:
    try:
        runoob()
    except AssertionError as error:
        print(error)
    else:
        try:
            with open('file.log') as file:
                read_data = file.read()
        except FileNotFoundError as fnf_error:
            print(fnf_error)
    finally:
        print('这句话，无论异常是否发生都会执行。')
    raise()语句:raise [Exception [, args [, traceback]]];(让代码报错,触发异常)
    x = 20
    if x > 15:

    raise Exception('x 不能大于 15。x 的值为: {}'.format(x)) 
    输出异常:#Traceback (most recent call last):
      File "test.py", line 3, in <module>
        raise Exception('x 不能大于 15。x 的值为: {}'.format(x))
    Exception: x 不能大于 15。x 的值为: 20