A technique from a chatbot

[Mark Bourne]

Thomas Passin wrote:
> On 4/2/2024 1:47 PM, Piergiorgio Sartor via Python-list wrote:
>> On 02/04/2024 19.18, Stefan Ram wrote:
>>>    Some people can't believe it when I say that chatbots improve
>>>    my programming productivity. So, here's a technique I learned
>>>    from a chatbot!
>>>    It is a structured "break". "Break" still is a kind of jump,
>>>    you know?
>>>    So, what's a function to return the first word beginning with
>>>    an "e" in a given list, like for example
>>> [ 'delta', 'epsilon', 'zeta', 'eta', 'theta' ]
>>>
>>>    ? Well it's
>>> def first_word_beginning_with_e( list_ ):
>>>      for word in list_:
>>>          if word[ 0 ]== 'e': return word
>>>
>>>    . "return" still can be considered a kind of "goto" statement.
>>>    It can lead to errors:
>>>
>>> def first_word_beginning_with_e( list_ ):
>>>      for word in list_:
>>>          if word[ 0 ]== 'e': return word
>>>      something_to_be_done_at_the_end_of_this_function()
>>>    The call sometimes will not be executed here!
>>>    So, "return" is similar to "break" in that regard.
>>>    But in Python we can write:
>>> def first_word_beginning_with_e( list_ ):
>>>      return next( ( word for word in list_ if word[ 0 ]== 'e' ), None )
>>
>> Doesn't look a smart advice.
>>
>>>    . No jumps anymore, yet the loop is aborted on the first hit
> 
> It's worse than "not a smart advice". This code constructs an 
> unnecessary tuple, then picks out its first element and returns that.

I don't think there's a tuple being created.  If you mean:
     ( word for word in list_ if word[ 0 ]== 'e' )

...that's not creating a tuple.  It's a generator expression, which 
generates the next value each time it's called for.  If you only ever 
ask for the first item, it only generates that one.

When I first came across them, I did find it a bit odd that generator 
expressions look like the tuple equivalent of list/dictionary 
comprehensions.

FWIW, if you actually wanted a tuple from that expression, you'd need to 
pass the generator to tuple's constructor:
     tuple(word for word in list_ if word[0] == 'e')
(You don't need to include an extra set of brackets when passing a 
generator a the only argument to a function).

-- 
Mark.