plain kindle
def is_leap_year(year):
if year % 4 == 0:
if year % 100 == 0 and year % 400 != 0:
return "This year is NOT a leap year."
elif year % 100 == 0 and year % 400 == 0:
return "This is a leap year! Now you get to suffer 1 more day than usual!"
else:
return "This year is Not a leap year"
print(is_leap_year(int(input("What year is this?"))))
I'm really new to python, so I'm sorry if i'm being a dumbass, I've yet to understand how the "return" function works...
icy plazaBOT
def is_leap_year(year):
if year % 4 == 0:
if year % 100 == 0 and yea...
@plain kindle
Python help channel opened
grand jackal
def is_leap_year(year):
if year % 4 == 0:
if year % 100 == 0 and yea...
What year are you testing with?
plain kindle
I'm trying to take the user's input and to do some math with that input.
So it's not a specific year
grand jackal
any function that doesn't reach its return will have a value of None
plain kindle
Sorry if i'm confusing you! :(
grand jackal
so something is wrong with your conditions where none of the return paths are being followed
Let's look closely at your conditions
plain kindle
any function that doesn't reach its return will have a value of `None`
I don't understand this fully...
grand jackal
if year % 4 == 0:
this checks if the year is divisble by 4
and this looks good
but then you add two extra conditions after to check for
if year % 100 == 0 and year % 400 != 0:
return "This year is NOT a leap year."
if the year is divisible by 100 but NOT by 400, return that it isn't a leap year
!e
def is_leap_year(year):
if year % 4 == 0:
if year % 100 == 0 and year % 400 != 0:
return "This year is NOT a leap year."
elif year % 100 == 0 and year % 400 == 0:
return "This is a leap year! Now you get to suffer 1 more day than usual!"
else:
return "This year is Not a leap year"
year = 1700
print(is_leap_year(year))
:white_check_mark: Your 3.12 eval job has completed with return code 0.
This year is NOT a leap year.
if we test with 1700, we can see that this works as intended
elif year % 100 == 0 and year % 400 == 0:
return "This is a leap year! Now you get to suffer 1 more day than usual!"
then you check if it's divisible by 100 AND 400
there's really no need to check for both
if it's divisible by 400, then of course its also divisible by 100
plain kindle
ooooh
grand jackal
but
even this check is not necessary
by the time the code reaches this point, we've already established that the year is divisible by 4
and we've already established that the year is not divisible by 100 but not 400
which means, all years that have made it this far must be leap years
however, there's still a flaw with the overall design of this function
is_leap_year is a function that should return True for leap years and False for non-leap years
you aren't returning True or False, you're returning strings
plain kindle
oh, so I should use booleans more often here?
grand jackal
don't look at it as "use them more often"
generally functions that begin with is will return True or False
we're checking if something is True or False
plain kindle
generally functions that begin with `is` will return True or False
With "is"? I guess i haven't gotten that far yet.
grand jackal
it's just a naming convention
it doesn't force anything
look at string methods for example
!e
print(*[i for i in dir(str) if i.startswith('is')], sep=', ')
:white_check_mark: Your 3.12 eval job has completed with return code 0.
isalnum, isalpha, isascii, isdecimal, isdigit, isidentifier, islower, isnumeric, isprintable, isspace, istitle, isupper
don't worry about the code, just look at the result
these are all the string methods that begin with is
they all check if a string contains specific characters. These all return bool
plain kindle
Oh, so if a function begins with an "is" It'll return either "True" or "False"?
grand jackal
it's not mandatory, but it's a pretty reliable rule
plain kindle
!e
```py
print(*[i for i in dir(str) if i.startswith('is')], sep=', ')
```
Though frankly I don't quiet understand what's this line of code does...
plain kindle
o
grand jackal
so you said you're still not quite sure what return does?
plain kindle
Yup, I've just learned about it yesterday, but as far as I've seen, a lot of codes use this function.
grand jackal
in your own words, what would you say a function is used for?
plain kindle
return marks an end of a function, that's one
grand jackal
I'm not interested in the syntax. What is a function?
What does it do? What would you need one?
grand jackal
I'm not asking about what return is. I'm asking about what a function is.
plain kindle
oh
sry
function is a specific set of various... acts...?
idk how to properly say this)
grand jackal
That's ok, I'm just trying to work out what you know and how well you know it
A function is simply a pre-defined set of instructions that we can then run later
plain kindle
yup, there's also an input function, like "this_stuff(stuff2, stuff3)"
grand jackal
I wouldn't refer to that as an input function
defining your own functions are kind of a 2 step thing
step 1 is defining it
and step 2 is calling it
plain kindle
oh, oke
grand jackal
def foo():
print("function foo is being called")
first we define it
if we ran this, it would appear that nothing happens
plain kindle
yup
grand jackal
!e
def foo():
print("function foo is being called")
:warning: Your 3.12 eval job has completed with return code 0.
[No output]
foo()
grand jackal
exactly
plain kindle
then it would actually run
grand jackal
!e
def foo():
print("function foo is being called")
foo()
foo()
foo()
:white_check_mark: Your 3.12 eval job has completed with return code 0.
001 | function foo is being called
002 | function foo is being called
003 | function foo is being called
functions are also nice because we can reuse them as many times as we want
it really helps you cut down on writing repetitive code
plain kindle
yup, and not to print gigantic code :D
grand jackal
ok, so it's important to understand that printing has no value
it's a function used to display output
when you're a beginner, pretty much everything you do is going to be focused on trying to print some sort of result
plain kindle
ok, so it's important to understand that *printing* has no value
Like... You can't set a specific value to it like you can to a variable?
grand jackal
but as you write more and more advanced code, the goal won't always be to print something
let's say I want to write a script that takes every image in a folder and shrink it by 50%
that doesn't really require any printing
grand jackal
!e
x = print(123)
:white_check_mark: Your 3.12 eval job has completed with return code 0.
123
if I were to do print(x) on the next line, what do you think would happen?
plain kindle
It would print 123 again, perhaps? Because you've already set a variable called "x", where you print a specific number
grand jackal
that's not quite how functions work
plain kindle
:(
grand jackal
when we do x = print(123), we aren't storing the function call in the variable
plain kindle
ooh
plain kindle
and EVERY function has a return
?
grand jackal
whatever is returned basically replaces the call
any function that doesn't directly provide a return will automatically return None
print always returns None
let's look at a better example
def foo():
return 5
this isn't a very exciting function, but what's important is that it returns 5
def foo():
return 5
result = foo()
It's like I sot of understand it, so if a function returns something then it's basically like calling a function?
grand jackal
the way a function is called doesn't change whether or not it has a return
returning None is still a return
it's just not a useful return
plain kindle
it's just not a *useful* return
aha, yup:)
grand jackal
```py
def foo():
return 5
result = foo()
```
look closely at this
foo() gets called
it returns 5
so foo() will essentially become the value 5 when it is called
result = foo()
as far as python is concerned here, all it sees is result = 5
the value gets returned to the caller
plain kindle
ooh, so, basically "foo =5"?
grand jackal
!print-return
icy plazaBOT
grand jackal
Watch this gif a few times
mighty loom
Hey @grand jackal ... when you finish can you please come to the My pygame game keeps free....
grand jackal
Hey <@143878644169834496> ... when you finish can you please come to the My pyga...
Sorry I don't know pygame
mighty loom
ok
plain kindle
oooh, so, basically, my_function is set at 5, then the computer sees a that y = my_function, so it does manipulation inside this function
grand jackal
whenever we call a function, we simply run the code inside the function until it reaches a return
then whatever is returned becomes the value where it was called from
grand jackal
are you familiar with the len() function?
plain kindle
so you can kinda say, that my_function = 7>
plain kindle
are you familiar with the `len()` function?
sort of yes, the length of a specific... thing.
grand jackal
sort of yes, the length of a specific... thing.
exactly. It returns the length of a thing
plain kindle
I've used it on strings mostly
plain kindle
exactly. It *returns* the length of a thing
OOOOO
grand jackal
!e
result = len('abcde')
print(result)
:white_check_mark: Your 3.12 eval job has completed with return code 0.
5
the len function is called on the string 'abcde'. It goes and finds out how long the string is, and returns 5
so result = 5
plain kindle
so it sets a specific value to a, let's say, string, and then the user can use the data, that's outputted from it!?
grand jackal
exactly
returning is how we can use a function to do some sort of calculation, and then give us the result
plain kindle
so the user can basically "create their own len()"?
grand jackal
you can create whatever you can think of 🙂
plain kindle
well, yeah)))
grand jackal
for example, a function that checks whether or not a year is a leap year
year = 2024
result = is_leap_year(year)
and then we can, through different math manipulations, print out "result" and it will RETURN in a boolean?
grand jackal
remember the goal isn't always to print
plain kindle
oh yeah
grand jackal
maybe we want to clean up all the files on our computer
and we want to delete all files created in a leap year
plain kindle
then the print function will be rendered obsolete in this particular case
grand jackal
for file in files:
year = file.get_year()
if is_leap_year(year) is True:
file.delete()
this isn't quite real method names, but it's to give you an idea
plain kindle
I see
grand jackal
look at every file
get the year of the file
check if the year is a leap year
if it is, delete it
you can see here we don't always need to store the return in a variable
I'm just directly doing if is_leap_year(year)
plain kindle
oke, oke
grand jackal
The biggest problem in your original code is that not all paths led to a return
plain kindle
So the biggest problem with the original code is: 1 - sets too many unneseccary checks
that can be avoided
i see
K, with that knowledge in mind i'll try to fix it. But before I go, may I ask you a question that's sort of unrelated to this?
grand jackal
def check_name(name):
if name == 'timmy':
return True
elif name == 'sally':
return True
result = check_name('bob')
look at this simple example
plain kindle
ooh
grand jackal
this function only returns True if your name is timmy or sally
if your name is bob, nothing gets returned
grand jackal
K, with that knowledge in mind i'll try to fix it. But before I go, may I ask yo...
Sure
plain kindle
i see
plain kindle
Sure
I'm just concentrated on learning things on my own and I kinda feel like I'm cheating by using methods like these, are my fears not justified?
grand jackal
Methods like what? Discord help?
plain kindle
yup
grand jackal
How would it be cheating?
I didn't directly hand you the answer
you learned something new
and now you can take what you learned and try to apply it to your own code
asking questions is a great way to learn
as long as you continue to practice what you learn, you'll be ok
plain kindle
Thank you! I'm really new to all of this, so it does feel a little overwhelming, but it's interesting as heck! Thx once again! :D
grand jackal
Thank you! I'm really new to all of this, so it does feel a little overwhelming,...
Yeah it's a lot to take in! That's why questions are good, because it can hopefully help you focus on what's important
plain kindle
Yuipee! I did it :D And now I also understand the functions better!!! This was a hard coding challenge ngl)
grand jackal
Yuipee! I did it :D And now I also understand the functions better!!! This was a...
🎉
icy plazaBOT
Python help channel closed