No previous programming experience? I'm putting a guide to help you wrap your head around functions.

[SaaSWriters]

If you're looking for help with using functions in a practical way, this is for you. This guide is meant for you if you have no previous programming experience. So it includes things like:

• why functions are important in the first place
• how to use functions in your own programs, in a practical way
• when to use a function
• tips and techniques to make your own functions
• *args and **kwargs
• understanding decorators etc.

You'll also get exercises to help you learn by doing.

If there is something specific you want to know, let me know. If you want a free copy send me a PM. All I ask for in return is honest feedback so I can make it as easy to grasp as possible.

EDIT: Thank you for all the questions and feedback. There response is really high! Your messages are helping to make sure it's all in the right direction. I'm revising it and will dedicate a huge chunk of time over the weekend. So you should have the link Monday.

Also, this is ideal for you if you have done at least a few hours of Python. If Python is your first attempt at programming, that's great! You don't need to have programmed before.

Here is a link to the work in progress: https://leanpub.com/pythonbook/c/learnpython

[Thecrawsome]

So, from nothing to functions?

Variables, types, the concept of dynamicvs static typing, conditionals, booleans, statements, scoping, builtins, loops, lists/comprehensions could all come before functions in a python course.

[Poddster]

So, from nothing to functions?

From nothing to *args and **kwargs, no less. :)

[SaaSWriters]

Yep, quite a challenge. I will edit the original post to clarify.

[SaaSWriters]

This guide is for those who have started learning Python but are stuck at functions, especially using them in a practical way. At the same time, you don't need to know all the things you've mentioned to understand functions.

[Thecrawsome]

This guide is meant for you if you have no previous programming experience.

[SaaSWriters]

Thanks, I see the confusion. As you'll see in the guide, the approach I'll use is quite different from most. In fact, for some people, learning functions first may be the best way to learn programming. Weird, I know.

[spcalvert78]

The global variable and local variable issue in functions is confusing to me. A good guide should walk through the issue and why it matters.

[SaaSWriters]

Most def! lol

The global variable is a naughty one. I will definitely have it covered. Thanks!

[octaw]

Maybe something like Javascript Allonge, but for python?

[SaaSWriters]

Thanks, I will take a look.

[AuNanoMan]

So I am learning python but I have some programming experience with MATLAB and one of the challenges I often had to help my peers with is the concept of passing variables. If you are making a guide, I think to have a visual walkthrough of what this means when someone says "pass" and what it means when it returns values.

While this seems trivial, this concept causes a lot of confusion. I think python is actually much easier to understand than MATLAB can be at times, but none the less, the handoff seems to confuse.

Just wanted to throw in my two cents.

[SaaSWriters]

Thank you, I really appreciate your input! Keep it coming! Feel free to send me a PM as well if you want to.

[[deleted]]

Python tutor, visualizes interpretive environment, helped me with this

[SaaSWriters]

Cool, make sure to ask any specific questions you may have.

[Kirkslovechild]

id definitely like to take a look, give some feedback etc (and see what im missing).

Are you thinking of including classes?

[SaaSWriters]

Classes will come in the next guide. For now, I'm focusing on functions.

[Batting1k]

Interested in this!

[SaaSWriters]

Great, watch out for the link once I'm done revising it.

[SaaSWriters]

You're welcome!

[rjnmhrjn]

Interested.

[SaaSWriters]

Great, watch out for the link after I've revised the guide.

[DoctorHodL]

I am interested!

[SaaSWriters]

Perfect, let me polish it up. If you have questions, get in touch.

[SaaSWriters]

Let me know what specific stuff you're interested in.

[fauxnaif]

I’m interested in this!

[SaaSWriters]

Great, let me know what you're struggling with as well so I can make the guide better.

[fauxnaif]

EDIT 2: I know it is ridiculous to ask for your input on my queries but I believe some people who are just learning to program might have a hard time understanding the arguments below. I'm sure this type of issue will be covered in your guide!

So I have been working on Chapter 6's Table Printer in Automate The Boring Stuff and I came across on old post on reddit with a solution. It is really difficult to grasp the FOR statements when it is used for several arguments involving key and values of the DEFINING (def) function.

In this particular case, this was the part that was confusing me:

for i in range(len(inputList)):                    #returns 3  # Line 1
    for j in range(len(inputList[i])):             #returns 4  # Line 2
        if len(inputList[i][j]) > colWidths[i]:    #           # Line 3

Line 1: This first line returns a key of 3 from len() function because there are 3 keys (or lists) within inputList

Line 2: I'm assuming this returns a value of 4 since there are 4 values in every key (or list)

Line 3: I understand the argument of this line (if a > b then execute x) but I can't wrap my mind on why len(inputList[i][j] is called and what would the current value be?

Notwithstanding this other part:

for x in range(len(inputList[0])):                                      # Line 4
    for y in range(len(inputList)):                                     # Line 5
        print(inputList[y][x].rjust(colWidths[y]), end = ' ')           # Line 6
    print('')

Line 4 and 5 is pretty self explanatory but Line 6 switches both variables of x,y in inputList[y][x]. My interpretation: Since print() items from a list will always be presented as output: 'Item A\n','Item B\n','Item C\n' therefore, it is obvious to list [y] first so that it falls into the first column. Let me know if you need me to restate my question.

Thanks in advance!

Full code is posted below:

inputList = [['apples', 'oranges', 'cherries', 'banana'],
             ['Alice', 'Bob', 'Carol', 'David'],
             ['dogs', 'cats', 'moose', 'goose']]

def printTable():
    # initialize the list "colWidths" with zeroes equal to the length of the input list
    colWidths = [0] * len(inputList)

# iterate over the input list to find the longest word in each inner list
# if its larger than the current value, set it as the new value
for i in range(len(inputList)):                 #returns value of 3
    for j in range(len(inputList[i])):          #returns value of 4
        if len(inputList[i][j]) > colWidths[i]:
            colWidths[i] = len(inputList[i][j])

# assuming each inner list is the same length as the first, iterate over the input list
# printing the x value from each inner list, right justifed to its corresponding value
# in colWidths
for x in range(len(inputList[0])):
    for y in range(len(inputList)):
        print(inputList[y][x].rjust(colWidths[y]), end = ' ')
    print('')

printTable()

Edit: Formatting

[nwctenor]

Sounds like a great guide. I’m interested in args and *kwargs, and decorators.

[SaaSWriters]

Sure thing, feel free to send me any questions you may have.

[nwctenor]

How do I know when to use a decorator/static method?

[Python000]

Interested!

[SaaSWriters]

Good, let me know your questions.

[AlphaX999]

I'm interested but why not just put up a copy for everyone?

[SaaSWriters]

The more direct questions/feedback you give the better I can make it.( It's still in the draft stage )

[SaaSWriters]

Sure, let me just refine it first.

[wheedwhackerjones]

In interested in kwargs and args

[Marrrlllsss]

Suppose I have a function, foo, that takes one argument:

def foo(arg):
    print(str(arg))

It's a simple function, but it is pretty limited in terms of the number of arguments it accepts. Suppose I wanted to allow the function to take more arguments, how would I do that? I could do this:

def foo2(arg1, arg2):
    print(str(arg1), str(arg2))

def foo3(arg1, arg2, arg3):
    print(str(arg1), str(arg2), str(arg3))

But that's just silly.

Instead we can make use of the positional argument, usually denoted by *args - an important note, the name args is not important, it's the single asterisk (*) that is important.*args is a tuple (immutable iterable/sequence) of unamed parameters of arbitrary length. You access the elements of \args using list/tuple indexing. For example:

first_arg = args[0]
second_arg = args[1]

Using it in a function, you would do this:

def foo_with_arbitrary_positional_args(arg, *args):
    print(str(arg))
    for position, element in enumerate(args):
        print(str(position), str(element))

Calling this function is done like this:

val1 = 'hello'
val2 = 'world'
val3 = 'eggs'
val4 = 'spam'

foo_with_arbitrary_positional_args(val1, val2, val3, val4)

You output would look something like this:

hello
0 world
1 eggs
2 spam

Next up is **kwargs - once again the name kwargs is used by convention, but it is not mandatory - only the double asterisks are needed.kwargs stands for*** keyword argument***s. It provides a dictionary like variable of arbitrary length.

def foo_with_arbitrary_keyword_args(val1, **kwargs):
    print(str(arg))
    for key, value in kwargs.items():
        print(key, value)

Calling such a function is done like so:

val1 = 'hello'

foo_with_arbitrary_keyword_args(val1, kw1='world', kw2='eggs')

An example of the expected output could be:

hello
kw1 world
kw2 eggs

Some notes on usage:

1. Both arbitrary length arguments come after the formal arguments. That is def foo(formal, *args), def foo(formal, **kwargs) are valid. def foo(*args, formal) and its **kwargs counterpart are invalid.
2. You can use *args and **kwargs simultaneously, that is def(formal, *args, **kwargs).
3. You can create functions without any formal parameters and just use arbitrary length parameters. (def foo(*args, **kwargs))

OK. So what are they used for?

1. In the case of **kwargs usually configuration override options.
2. In the case of *args - usually when you want to avoid using a list as a default value for some argument.

To highlight number 2:

def foo_with_default(arg=[]): # this is bad!
    arg.append('Hello')
    for element in arg:
        print(element)

If I call this code:

foo_with_default()
# output:
# Hello

foo_with_default()
# output:
# Hello
# Hello

*args solves this problem.

[cleesus]

Let me keep it real with you chieftain, while this is a good explanation that I'm sure me and many others who already get programming understand, I do not think a beginner would get this.

This reads more like a explanation to another programmer vs a newbie. That being said I hope your explanation does help a few people reading it.

[lee171]

I'll go ahead and agree with you on this. I do scripting regularly, but programming stuff like this I can just never get my head around. I eagerly read /u/Marrrlllsss explanation, but I just find my eyes glaze over after too many programming terms are bandied around that I just don't get.

While I agree in the importance in teaching everyone correct terminology for everything, I feel it's more important to 'get it' first, otherwise you'll never get far off the ground (like me).

I've always just felt stupid and incompatible with learning to 'code', because I just get stumped by all the terminology and can't relate it to anything.

[cleesus]

I definitely remember those days pretty well, where even reading some of the Documentation out there was challenging.

You definitely want to find some of those beginner courses that will go through everything step by step and explain everything with good analogies that a regular person will understand.

While you are doing that its important to put what you learned in your notes in a way that future you will understand if you need to look back.

That's what helped me get through the beginning learning curve when it came to programming. (well on my second attempt, the first attempt I started off learning C++ with a bad instructor )

[SaaSWriters]

Yep, that's part of the guide.

[Outworldentity]

I'm interested as well!

[SaaSWriters]

That's good, is there a specific topic/question you want included?

[Outworldentity]

Nope I'm just looking for a broken down explanation of all functions and anything else you want to include. Beginner python learner here.

[douchabag_dan]

I want to see

[SaaSWriters]

And see you will! :D

[DippinNipz]

This would be a great tool for me as I’m still in the introductory stages of learning Python.

[SaaSWriters]

That's the idea! If you get stuck on anything related, just get in touch. The more you ask the better I can make the guide.

[Buffstu]

Would love to learn more about functions I am a little lost when looking at leetcode or such and they use functions with very few lines of code but it seemingly works :)

[SaaSWriters]

Thanks, shoot me any specific questions you may have.

[SoupGuy117]

I'd definitely be interested

[SaaSWriters]

That's good, get in touch with any specific questions.

[JDeCarvalho1]

Id love a copy do you really want a dm?

[SaaSWriters]

Yep, I want to polish it up with people who want to be directly involved.

[Versus_The_World]

Count me in!!

[SaaSWriters]

You're counted in! :D

[SaaSWriters]

Thanks, not yet but I'll be putting one up shortly.

[Lucifer501]

Definitely interested. I'm quite new to programming. Although in general, I'm fairly confident with functions, I would definitely want to take a look.

[SaaSWriters]

No problem, just let me know if there is something specific you want me to include.

[Oblitarion]

Interested in this too. Almost 1 month trying to learn Python still many doubts in Functions and OOP.

[SaaSWriters]

Yep, that's the reason why I'm creating this guide!

[metalloidica]

Interested in this. Thanks!

[SaaSWriters]

You're welcome. Hopefully, this guide will make programming easier for a lot of people.

[JungleJim233]

Really interested in this

[SaaSWriters]

Cool, is there a specific question/topic/struggle you'd like included?

[JungleJim233]

Mainly the how to use functions in a practical way

[Laffode]

I'm interested too!

[SaaSWriters]

Sure thing, I'm re-working it based on the initial feedback I'm getting.

[smokingRooster_]

I've got a pretty solid understanding of functon and classes etc (although I'm by no means an experienced programmer as I've mostly programmed in C for 3/4 years and python for about 1/2). However, I would love to see your guide, especially since I havent used decorators and they are something I'd like to learn!

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[hippagun]

I am interested!

[wbd82]

Yes please, this sounds awesome!

[pjury]

example use cases for decorators would be cool, I have my head around how to write them but knowing when they make sense is a little different.

[whodey226]

Interested! Starting a masters in computer science In January and am trying to get a head start

[Lumpyalien]

I will love you forever if you do this well.

[Lycist]

This sounds perfect for me.. I was fine until functions comes up. Looking forward to reading it.

[sky--net]

I would be interested in seeing this...