Python常见的错误和异常讲解

检测和处理异常 上下文管理 触发异常 断言 标准异常

检测和处理异常

第一种语句：try-except

try:
    pass
except Exception, e: # 捕获所有异常
    raise e          # 抛出捕获的异常

第二种语句：try-except-except-except

try:
    pass
except Exception1, reason1:
    raise
except Exception2, reason2:
    raise
except Exception3, reason3:
    raise

第三种语句：处理多个异常的except语句

try:
    pass
except (Exception1,Exception2), reason:
    raise

第四种语句：try-except-else语句

try:
    pass
except Exception, e:
    raise e
else:    # try范围中没有检测到异常时，执行else语句
    pass

第五种语句：try-except-finally语句

try:
    pass
except Exception, e:
    raise e
finally: # 无论异常是否发生，是否捕捉到，都会执行该语句
    pass

第六种语句：try-except-else-finally

try:
    pass
except Exception, e:
    raise
else:
    pass
finally:
    pass

第七种语句：try-finally

try:
    pass
finally:
    pass

上下文管理

with open('/etc/pas','r') as f:
    for eachline in f:

触发异常

try:
    pass
except Exception, e:
    raise

断言

断言语句：如果断言成功不采取任何措施，否则触发断言错误的异常

assert 1 == 0

Traceback (most recent call last):
  File "E:\code\DA\da.py", line 5, in 
    assert 1 == 0
AssertionError