[Tutor] Fwd: Beginner struggling with python.

[Jack Simpson]

---------- Forwarded message ---------
From: Jack Simpson <simpsonrmz41 at gmail.com>
Date: Fri, 23 Jun 2023 at 1:58 pm
Subject: Re: [Tutor] Beginner struggling with python.
To: dn <PythonList at danceswithmice.info>


I tried to use the string.upper() and it returned this syntax error. I also
tried def upper() and upper(). I also tried underscores and spaces within
the string in the parenthesis which produced a similar result but the issue
was with the  code within the string. I am on a work computer using an
interpreter so please forgive the photos from my phone.

On Fri, 23 Jun 2023 at 12:51 pm, dn via Tutor <tutor at python.org> wrote:

> On 23/06/2023 12.07, Alan Gauld via Tutor wrote:
> > On 22/06/2023 22:45, Jack Simpson wrote:
> ...
>
> >> nicely until we got on to return values and defining functions. Are
> >> particular functions built into python such as def convert( etc.
>
> Yes, Python offers various built-in functions as well as the opportunity
> to write your own "custom functions".
>
> The 'built-ins' include len( string ) which will return the number of
> characters in the string - or number of elements in a "collection" when
> used with a list or similar.
>
> There are also 'functions' which are part of a data-type (class).
> Sticking with strings for the moment: string.upper() will ensure each
> character in that string is converted (where necessary) into
> upper-case/capital-letters. In Python, we use the term "everything is an
> object". So, this function is actually a "method" of the str[ing]
> type/class. There is an important difference between a function and a
> method - a method works on the value to which is is attached, eg
> "string" in this case, whereas a function works independently of any
> specific instance. (see "arguments" and "result" below - but this
> distinction is a bit curly for a beginner) You can tell which you're
> dealing-with, by the 'dotted-notation'.
>
> Then there are the functions you can write yourself, as @Alan has
> described.
>
>
> Noting that functions 'take in' certain (optional) values and return a
> result, the general form is:
>
> def name( arguments ):
>      # computation
>      return result
>
> The "name" should be a meaningful description of the "computation", ie
> the purpose of the function.
>
> The "arguments" (zero or more) will be a comma-separated list of
> identifiers which are inputs to the function. In @Alan's example, 7, to
> produce the seven times-table or 9 when your math is better than mine...
>
> The "computation" can be anything which Python will do for you.
> Sometimes we use a function to attend to a sub-problem within the wider
> application, ie produces a neatly labelled-result. Another use for
> functions is when we repeat the same "computation" repeatedly, and
> perhaps from different points in the application.
>
> The "result" seems self explanatory. Every function returns a "result".
> If there is a return-statement, that will compute a value. If not, the
> return-value is None. The wording in the singular-form is slightly
> mis-leading. If appropriate, a function can return a collection of
> values, eg a tuple or a list - however it is still only one "collection"!
>
>
> We don't have to def-ine built-in functions (or those which are
> import-ed from a library).
>
>
> The "name( arguments )" and "return result" components are often called
> the "signature" of the function. Basically, the function says: if you
> give me this, I'll give you that by-return. Hah! The "signature" is an
> interface which sets-out all the 'rules' for what you can do with the
> function - remember the len() example (above), its signature allows us
> to apply it to a string or a list (or other "collection"). Flexibility!
> ("polymorphism").
>
> The "signature" also advises what to expect as a result: OK the 'length'
> part is right there in the function-name, but the signature tells us
> that the return-value will be an integer. Again, not much of a surprise
> given that we are expecting a number, and it is hard to have a string
> with a negative-number of characters or indeed part of a character.
> However, some functions are less obvious and thus the signature is the
> means of ensuring that we use the function for the purpose and in the
> manner its author intended.
>
> In the Python REPL try: help( function_name )
> Web.Ref: https://docs.python.org/3/library/functions.html#len
>
>
> Using a function is termed "calling a function". As above, this can look
> like:
>
> number_of_characters = len( string )
> or
> seventh_times_table = times_table( 7 )
>
> The general form here is:
>
> identifier = function_name( parameters )
>
> The "signature" is also generalised, but is at-least specific to that
> particular function.
>
> Do we need to document that "function_name" has to correspond to a
> def-statement (either one of our own, or one built-in and provided to us)?
>
> The optional parameters must be provided if the function/signature
> demands. Some may be required. Others may be optional. There is a
> variety of ways these may be expressed (a story for another day).
>
> The function's return-value is passed 'across' the assignment to
> "number_of_characters" or "seventh_times_table" (or passed directly into
> the print() function*). The identifier will become the same data-type as
> the result-data.
>
> * you will have noticed that @Alan uses the function's result within a
> print-call rather than an assignment statement, but we are still making
> use of the return-value.
>
>
>
> (just because this very afternoon, I've been helping someone-else who's
> using it)
> A free-to-download or read-on-the-web book is Al Sweigart's "Automate
> the Boring Stuff". Chapter 3 deals with functions
> (http://automatetheboringstuff.com/2e/chapter3/)
> It's getting a bit old now, but the basics haven't changed...
>
>
> @Alan mentioned online tutorials, quite possibly anticipating that I'd
> chime-in with (an alternate/additional view): the suggestion of online
> courses, eg Coursera, edX, FutureLearn, ... The advantage of these is
> that they usually present their material in both text and video forms,
> plus they collect a community of fellow-trainees, who will help
> each-other with questions and readily-recognise which session/chapter
> you're working at, right now.
>
> (however, re-iterating @Alan's welcome, this Discussion List is also for
> exactly those kinds of discussions)
>
>
> Disclaimer: I use the edX platform - but not for Python training.
> --
> Regards,
> =dn
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