In [ ]:

    




    

In [2]:

    

# basic try/except
def is_int(val):
    try:
        x = int(val)
        return True
    except ValueError:
        return False

is_int('erik')


    

    
Out[2]:





False

In [3]:

    

# finally
def is_int(val):
    try:
        x = int(val)
        return True
    except ValueError:
        return False
    finally:
        print('done')
        
is_int('3')


    

    




done






    
Out[3]:





True

In [4]:

    

is_int('erik')


    

    




done






    
Out[4]:





False

In [11]:

    

def is_int(val):
    try:
        x = int(val)
        return True
    except ValueError as e:     #e is the handled exception
        print(e)
        return False

is_int('erik')


    

    




invalid literal for int() with base 10: 'erik'






    
Out[11]:





False

In [15]:

    

# multiple except blocks are tried in order, until a match is found
def is_int(val):
    try:
        x = int(val)
        return True
    except TypeError:
        print('caught TypeError')
        return False
    except Exception:
        print('caught Exception')  # this one is caught
        return False
    except ValueError as e:     
        print('caught ValueError')
        return False

is_int('e')


    

    




caught Exception






    
Out[15]:





False

In [14]:

    

# beause of above, you should order except blocks from most specific to least
def is_int(val):
    try:
        x = int(val)
        return True
    except ValueError:
        print('caught ValueError')
        return False
    except Exception as e:     
        print('caught Exception')
        return False

is_int('e')


    

    




caught ValueError






    
Out[14]:





False

In [16]:

    

# getting code to run if NO exception is raised
def is_int(val):
    try:
        x = int(val)
    except ValueError:
        print('caught ValueError')
        return False
    else:
        print('no error')
        return True

is_int('10')


    

    




no error






    
Out[16]:





True

In [17]:

    

# having two exceptions use the same except block
def is_int(val):
    try:
        x = int(val)
    except (TypeError, ValueError):
        print('caught ValueError or TypeError')
        return False
    else:
        print('no error')
        return True

is_int('erik')


    

    




caught ValueError or TypeError






    
Out[17]:





False

In [18]:

    

# catching all exceptions

def is_int(val):
    try:
        x = int(val)
        return True
    except Exception:    # use Exception, which handles all exceptions that are not supposed to automatically kill the app
        return False

is_int('erik')


    

    
Out[18]:





False

In [43]:

    

# raising a simple exception

def raise_on_non_string(val):
    if not isinstance(val, str):
        raise TypeError('Expected a string')
        
try:
    raise_on_non_string(34)
    
except Exception as e:
    print(e)


    

    




Expected a string

In [42]:

    

# catching an exception, wrapping it with your own and re-throwing
def wrap_raise_on_non_string(val):
    try:
        return raise_on_non_string(val)
    except TypeError as e:
        raise RuntimeError('Wrapping error....') from e


    

In [55]:

    

# catching and rethrowing
def wrap_raise_on_non_string(val):
    try:
        return raise_on_non_string(val)
    except TypeError:
        print('TYPE ERROR')
        raise

try:
    wrap_raise_on_non_string(34)
except Exception as e:
    print(e)


    

    




TYPE ERROR
Expected a string

In [ ]: