exception handling

#TypeError:intType is not iterative.
for i in 3:
    pass
#ValueError
num=input(">>: ") #Input hello
int(num)

#NameError
aaa

#IndexError
l=['egon','aa']
l[3]

#KeyError
dic={'name':'egon'}
dic['age']

#AttributeError
class Foo:pass
Foo.x

#ZeroDivisionError:Unable to complete calculation
res1=1/0
res2=1+'str'

2.Logical error

AttributeError Trying to access a tree with no object, such as foo.x, but foo has no attribute xIOError input/Output exception; basically unable to open file.ImportError cannot import modules or packages; basically, it is a path problem or a name error.IndentationError syntax error (subclass); code is not aligned correctly.Under IndexErrorThe index index exceeds the sequence boundary, for example, when x has only three elements, it tries to access x[.5]
KeyError Trying to access keys that do not exist in the dictionaryKeyboardInterrupt Ctrl+CBe pressedNameError uses a variable that is not yet assigned to an object.SyntaxError Python code is illegal, and the code can not be compiled.The type of TypeError incoming object is not consistent with the requirement.UNboundLocalError attempts to access an unset local variable, essentially because there is another global variable with the same name.Which leads you to think that it is visiting it.ValueError passes a caller's undesired value even if the type of the value is correct.

AGE=10
while True:
    age=input('>>: ').strip()
    if age.isdigit(): #Only when age is an integer in string form, the following code will not go wrong. The condition is predictable.
        age=int(age)
        if age == AGE:
            print('you got it')
            break

#The basic syntax is
try:
    Code blocks detectedexcept Exception type:Once an exception is detected in try, the logic of the location is executed.#Give an example
try:
    f=open('a.txt')
    g=(line.strip() for line in f)
    print(next(g))
    print(next(g))
    print(next(g))
    print(next(g))
    print(next(g))
except StopIteration:
    f.close()

#1 Exception classes can only be used to handle specified exceptions. If no exception is specified, it can not be processed.
s1 = 'hello'
try:
    int(s1)
except IndexError as e: # The exception was not captured, and the program was directly reported.
    print e

#2 Multi branch
s1 = 'hello'
try:
    int(s1)
except IndexError as e:
    print(e)
except KeyError as e:
    print(e)
except ValueError as e:
    print(e)

#3 Universal exception Exception
s1 = 'hello'
try:
    int(s1)
except Exception as e:
    print(e)

#4 Multiple branch anomalies and omnipotent anomalies
#4.1 If the effect you want is that no matter what happens, we discard them all together, or use the same piece of code logic to handle them, then Sao Nian, do it boldly, just one Exception is enough.
#4.2 If you want the effect that we need to customize different processing logic for different exceptions, you need to use multiple branching.

#5 It can also be multiple branches later on a Exception.
s1 = 'hello'
try:
    int(s1)
except IndexError as e:
    print(e)
except KeyError as e:
    print(e)
except ValueError as e:
    print(e)
except Exception as e:
    print(e)

#6 Other institutions of exception
s1 = 'hello'
try:
    int(s1)
except IndexError as e:
    print(e)
except KeyError as e:
    print(e)
except ValueError as e:
    print(e)
#except Exception as e:
#    print(e)
else:
    print('tryIf I have no exception in the code block, execute me.')
finally:
    print('Whether abnormal or not, the module will be executed, usually cleaning.')

#7 Active trigger exception
try:
    raise TypeError('error in type')
except Exception as e:
    print(e)

#8 Custom exception
class EgonException(BaseException):
    def __init__(self,msg):
        self.msg=msg
    def __str__(self):
        return self.msg

try:
    raise EgonException('error in type')
except EgonException as e:
    print(e)

#9 Assertion: assert condition
assert 1 == 1  
assert 1 == 2

#10 Sum up try..Except

1：Separate the error handling from the real work.2：Code is more organized, clearer, and complex tasks are easier to achieve.3：There is no doubt that it is safer, so that the procedure will not crash due to minor negligence.