🔒 Program to find the series

[torn wolf]

Im a beginner and Im so lost with this homework question

[rugged nimbus]

@torn wolf

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[serene mauve]

What have you gotten so far? @torn wolf

[torn wolf]

x=float(input("Enter x: "))
n=int(input("Enter N: "))
s=0

is all i got 😭

i think we have to use a for loop but im not sure

[serene mauve]

Could use a for loop sure, do you have any idea how to start with that?

[torn wolf]

maybe like
for i in range(1,n+1)

[serene mauve]

That is fine

And could you express a single term.

So the first term is

+x

then

-x^2 / 2!

then

+x^3 / 3!

etc.

What is the pattern?

[torn wolf]

the exponent and the denominator

gets increased

[serene mauve]

So let us use i to denote the term number

What patterns do you see

• and -, what is the pattern?

[torn wolf]

oh it changes every time

[serene mauve]

How could we make it clear when it is +, en when -?

[torn wolf]

could we do like even - and odd +?

[serene mauve]

if ... the term is postive, else the term is negative

[torn wolf]

ohhh

[serene mauve]

What do you fill in there?

Given i

[torn wolf]

im not sure but like is it

for i in range(1,n+1):
if x%2==0:

[serene mauve]

We do not have x defined

[torn wolf]

but like x is given by user right?

[serene mauve]

Ah like that

but still, whether the term is even or odd, has nothing to do with x

But with i

for i in range(1,n+1):

Here we go through each term number, where i is set to the term number each iteration.

1 then 2 then 3, etc.

[torn wolf]

so do we say n instead of x?

oh no wait its i itself

we use

i think

[serene mauve]

Yes

[torn wolf]

wait so we use i or n?

[serene mauve]

n does not change

[torn wolf]

ohhhhh

[plain nimbus]

n is just the upper limit for your i

[torn wolf]

ohh thank u

[serene mauve]

When we do

for i in range(1, n + 1):
  #code

It's like doing

i = 1
# code
i = 2
# code
i = 3 
# code
...
i = n
#code

[torn wolf]

ohhh

so we the statement would be like

[serene mauve]

And in # code we can make use of i

[torn wolf]

for i in range(1,n+1):
if n%2==0:

[serene mauve]

!e

n = 5
for i in range(1, n + 1):
  print(n)

[rugged nimbus]

:white_check_mark: Your 3.12 eval job has completed with return code 0.

001 | 5
002 | 5
003 | 5
004 | 5
005 | 5

[serene mauve]

!e

n = 5
for i in range(1, n + 1):
  print(i)

[rugged nimbus]

:white_check_mark: Your 3.12 eval job has completed with return code 0.

001 | 1
002 | 2
003 | 3
004 | 4
005 | 5

[torn wolf]

ohh i see

so its just prints all the digits

till n

[serene mauve]

I assume you haven't learned about lists yet?

[torn wolf]

no we havent started yet

[serene mauve]

Ah okay. You can see range as some array/list/sequence of values like range(1, 5) is basically [1, 2, 3, 4]

And by doing for i in range(1, 5) it basically iterates through every value

[torn wolf]

is it possible to write

range(5)

?

[serene mauve]

The start is 0 by default

so range(5) is range(0, 5)

[torn wolf]

ohh can we go in reverse too? like going backwards

[serene mauve]

If youw ant yes, the parameters are range(start, stop, step)

[torn wolf]

ohh but like if i say range(5), it will only print till 4

so if i want to have 5 in the list i need say 6 instead right??

[serene mauve]

!e

print(*range(10))
print(*range(1, 10))
print(*range(1, 10, 2))
print(*range(10, 1, -1))

[rugged nimbus]

:white_check_mark: Your 3.12 eval job has completed with return code 0.

001 | 0 1 2 3 4 5 6 7 8 9
002 | 1 2 3 4 5 6 7 8 9
003 | 1 3 5 7 9
004 | 10 9 8 7 6 5 4 3 2

[serene mauve]

Yes

[torn wolf]

ohh thank u this topic was very hard for me 😭

[serene mauve]

Yeah nws. I don't really get why teachers teach for loop before teaching lists

They just copy each other and do whatever is common for other languages, doesn't make sense

[torn wolf]

yeah its very confusing

[serene mauve]

Just remember this part for now

[torn wolf]

alr 🫡

[serene mauve]

So i' ll help a bit further

for i in range(1, n + 1):
  # If i is even
  if i % 2 == 0:
    ...
  # Else i is odd
  else:
    ...

With this if statement you can know if you are dealing with an even term, or odd term

[torn wolf]

ohh ok ok

[serene mauve]

i = 1

+x

i = 2

-x^2 / 2!

i = 3

+x^3 / 3!

etc.

We want to define something that makes it + or -

One easy way would be to define some multiplier multiplier and then set it to 1 or -1

Based on whether i is even or odd

[torn wolf]

oh

[serene mauve]

So fill in the dots

[torn wolf]

stupid doubt but can we put a for loop inside an if statement?

[serene mauve]

Yes

You can put an if statement in a for loop, a for loop in an if statement, an if statement in an if statement, a for loop in a for loop etc.

When I code I normally have an extra .py file open so I can just test this kinda stuff

You don't break the computer (easily) by just running some code you wrote, so just try this kinda stuff out

[torn wolf]

if i%2==0:
for j in range(1,(i*i) + 1):
term=x**j/x

im 100% this is wrong but this is what i think the blank is

[serene mauve]

Split the problem up

[torn wolf]

meaning?

[serene mauve]

^

Do what I said here

[serene mauve]

^

[torn wolf]

oh okay okay

[serene mauve]

We will first deal with - and +, then the denominator, then the numerator.

[torn wolf]

so under the if statement

we want the sign to be -

[serene mauve]

You can click the three ... click copy text, and fill it in.

[torn wolf]

i have no clue 😭

like how to mkae

the sign -

for even

[serene mauve]

Read the messages under the snippet of code

[torn wolf]

so like i*=-1

??

[serene mauve]

No, like what I described here. But I have to go now, sorry.

[plain nimbus]

I can try to help for a bit, could you show where you are currently at? I stopped following the thread ^^

[torn wolf]

no no its fine, i understood a lot

and thank u sm!!

[torn wolf]

ofc!

so we did this

for i in range(1, n + 1):

If i is even

     if i % 2 == 0:
...

Else i is odd

     else:
...

and basically im trying to figure out to fill in the blanks

the question is this btw

[plain nimbus]

Ah okay, so you need to calculate your individual terms then

[torn wolf]

yes so

i think in if statement

[torn wolf]

i have to do something like this

so do i just make a term and set it equal to -1 under if statement

[plain nimbus]

Yeah you could do that, or just subtract it instead of adding it. All perfectly fine ways to do this.

So now we need to figure out how to calculate the individual values.

[torn wolf]

oh ok

[plain nimbus]

Lets disregard the first one since that is a special case we can handle later, how would you calculate one of these using the values you have so far?

[torn wolf]

theres no values cause its based on what the user inputs

[plain nimbus]

Yeah, but in your code you have variables in place of your user input. You can use these to create a formula that will calculate the values based on user inputs.

You already have that in your loop, with n. Which doesn't have a value until the user gives it one

But to write code that calculates your result you have to assume you already have values for x and n.

Sorry if this is confusing... I feel like my explanation is not very clear. Let me try again.

[torn wolf]

no no i get it

we basically

have to sort make like an equation

with n and x is what i think

[plain nimbus]

Yes exactly

[torn wolf]

u trying to say

?

ohh

[plain nimbus]

Though you would use i and x.
Remember you want to iterate over all the terms and n just ist the value for your last term (and the limit for i)

[torn wolf]

ohh yeahh

so will the equation sort of be like
-x^i/i

for even

[plain nimbus]

Well 3! != 3 but essentially you would be right

You equation is (-)x^i/i!
Now you just need to figure out how to write that in python.

[torn wolf]

do we have to write like i! for more accuracy

just in case

?

[plain nimbus]

i! means factorial of i. Are you familiar with what factorial does?

It's the product of all numbers up to that number, so 3! = 1 * 2 * 3

[torn wolf]

it multiples from 1 to that number right?

[torn wolf]

oh so like for loop but mulitplicatino

[plain nimbus]

Yes

[torn wolf]

so in python

the equation (-)x^i/i!

would be like (-x**i)/

wait how do u write factorail in python

?

[plain nimbus]

xD

Yeah I was witing for this.

So since you are practicing loops I suggest you try writing it yourself

||But there is a function you can import

from math import factorial

that would also do give you a factorial||

[torn wolf]

im so clueless 😭

i have no idea how factorial statement is

[plain nimbus]

Well you already kinda said it

[torn wolf]

is it like factorical()

im guessing tbh lol

[torn wolf]

oh wait nvm

[plain nimbus]

Yes, generally there is no need to reinvent the wheel, if there is already a working solution.
The exception to this is when learning because writing these things for yourself can teach you a lot

So just disregard that for now. I just wanted to show you there would be an easy way you can use in the future.

[torn wolf]

ohh

so the statement will be like

(-x**i)/from i import factorial???

[plain nimbus]

nono forget the import

You never saw that 😉

[torn wolf]

OH ALR LOLL

[plain nimbus]

It's too early for you to worry about imports and stuff

[torn wolf]

so the factorical in python is like factorical()?

[plain nimbus]

No, python does not have a factorial by default

[torn wolf]

makes sense im suffering with loops already

[plain nimbus]

So you would have to make it yourself

[torn wolf]

OHH

so like f=f*i

?

[plain nimbus]

You still need a loop for factorial

[torn wolf]

so do we make another loop

under if the if statement

??/

[plain nimbus]

remember 5! = 5 * 4 * 3 * 2 (* 1)

[torn wolf]

ohh

[plain nimbus]

Do you know how functions work? If not dont worry about it.

[torn wolf]

no 😭

im very clueless abt a lot of thigns in python

[plain nimbus]

Dont worry

Everyone starts somewhere

[torn wolf]

wait so is f=f*i wrong?

[plain nimbus]

Yes

[torn wolf]

help whats the mistake 😭

[plain nimbus]

well its part of the solution, but you need to do that step more than once

[torn wolf]

ohh okay

[plain nimbus]

Also f=f*i doesn't work if f is undefined

And I don't remember if we defined f somewhere

[torn wolf]

so do we state f=1

before the loop

?

[torn wolf]

it wasnt

[plain nimbus]

Well you can do that, but remember in a typical for loop you already get a variable that increases every iteration, so you don't need to define it beforehand.

for f in ... would do what you need

What you will need however is a variable to store your result (i guess if f was meant for that then you would be correct)

[plain nimbus]

Ah yeah, you're right

[torn wolf]

oh okay

so the statement would go like

for i in range(1,n+1):
        if i%2==0:
              f=f*i
              (-x**i)/f```

[rugged nimbus]

Hey @torn wolf!

It looks like you pasted Python code without syntax highlighting.

Please use syntax highlighting to improve the legibility of your code and make it easier for us to help you.

To do this, use the following method:
```py
print('Hello, world!')
```

This will result in the following:

print('Hello, world!')```
You can **edit your original message** to correct your code block.

[plain nimbus]

No, you will need a 2nd for loop for your factorial.

[torn wolf]

so like another for loop

with a different variable or we use f itself

[plain nimbus]

Since you want to hold your result in f you need to use a new variable a the "counter" (also "index" - that's why it's usually named i) in your loop

However here you can't use i since your 1st loop already uses it.

[torn wolf]

oh so like for j in range(1,i+1):
f=f*j

[plain nimbus]

Yes

[torn wolf]

and then under the for j loop itself we put the equation right?

[plain nimbus]

You could even start you range at 2 range(2, i + 1) since f = f * 1 wont change your f. But thats very nitpicky and wont impact your programm overall

[plain nimbus]

correct

[torn wolf]

wait when u mean by 2 meaning like instead of starting at one, it goes like 2 3 4 right?

[plain nimbus]

yeah

[torn wolf]

ohh

[plain nimbus]

Also you need to "reset" f before your inner loop, the best place would be right before your 2nd for loop

[torn wolf]

for i in range(1,n+1):
        if i%2==0:
              for j in range(1,i+1):
                       f=f*j
                       (-x**i)/f```

[rugged nimbus]

Hey @torn wolf!

It looks like you pasted Python code without syntax highlighting.

Please use syntax highlighting to improve the legibility of your code and make it easier for us to help you.

To do this, use the following method:
```py
print('Hello, world!')
```

This will result in the following:

print('Hello, world!')```
You can **edit your original message** to correct your code block.

[torn wolf]

wait how do u reset?

like do we write f=1 after the print the equation

?

[plain nimbus]

Yeah you just reassign 1 to f before the loop ```py
for i in range(1, n + 1):
if i % 2 == 0:
f = 1
for j in range(1, i + 1):
f = f * j
(-(x**i)) / f

[torn wolf]

ohh okayy

even=(-(x**i)) / f
print(even)

and then its over for even right?

[plain nimbus]

Also let's restructure a bit py for i in range(1, n + 1): f = 1 for j in range(1, i + 1): f = f * j if i % 2 == 0: (-(x ** i)) / f
You will need the factorial regardless of your if statement, you you can calculate it before that (avoids repetition and unnecessary indents)

[torn wolf]

but if we do like that then wont it be hard to do for the odd digits?

or is that still possible?

ohh wait

i got it

i understood

[plain nimbus]

That will actually make it easier for the odd digits, since you don't need the code to calcualte the factorial again

[torn wolf]

true

so basically we first do the caluclate for the factrical

and then do the equation

[plain nimbus]

calcualte
I can't spell this word for the life of me...

[torn wolf]

dw my spelling is even worse 😭

[plain nimbus]

Yes, factorial first and then the equation.

[torn wolf]

n=int(input("Enter value of N: "))
for i in range(1, n + 1):
    f = 1
    for j in range(1, i + 1):
        f = f * j
    if i % 2 == 0:
        even=(-(x ** i)) / f
        print(even)
    else:
        odd=(+(x**i))/f
        print(odd)```

[rugged nimbus]

Hey @torn wolf!

It looks like you pasted Python code without syntax highlighting.

Please use syntax highlighting to improve the legibility of your code and make it easier for us to help you.

To do this, use the following method:
```py
print('Hello, world!')
```

This will result in the following:

print('Hello, world!')```
You can **edit your original message** to correct your code block.

[plain nimbus]

Looks good so far, almost there

[torn wolf]

so after this what do we do?

[plain nimbus]

Well this only gives you the values of your individual terms, not the value of the series.
So you need to add all those single values together

[torn wolf]

ohhh

so we need to make a statement where it adds all the even and odd right?

[plain nimbus]

I would recommend the add a variable outside of your loop that you could then use to collect all of your values. (called result or something so you know it contains your final value)

[torn wolf]

so like result=1?

[plain nimbus]

Why 1?

Does your series start with 1?

[torn wolf]

uh no i think 😭

[torn wolf]

i think its one cause in the loop it goes from one to n+1

so i thought result would also be one?

[plain nimbus]

Hmm I think the result should be 0, since your series is "empty" when you start your calculations. It only gets a value when you add to it

[torn wolf]

oh yeah true

[plain nimbus]

result here is essentialy S in your original screenshot

[torn wolf]

so do we write result=0 in the for i loop

or out of it

[plain nimbus]

Out of it, you wouldn't want to reset your result while calculating the series

[torn wolf]

alr 🫡

so in the for i loop

do we just write result= even + odd?

[plain nimbus]

No you cannot do that, let me explain why.

In an if/else statement only one of the two code blocks will execute, the variable coming from the other will not be defined and raise an Exception (crash your program)

And even if that wasn't the case you dont want to add both values every loop

[torn wolf]

ohh

wait so how can we add it then?

[plain nimbus]

So you have 2 options (give me a minute)

[torn wolf]

ofc!

[plain nimbus]

# option 1: add them twice
if i % 2 == 0:
    even = (-(x**i)) / f
    result += even
else:
    odd = (+(x**i)) / f
    result += odd

# option 2: store the result in the same variable
if i % 2 == 0:
    term = (-(x ** i)) / f
else:
    term = (+(x ** i)) / f
result += term```
"+=" means in place addition.
So `a += b` is equal to `a = a + b` (just a nicer way of writing it, they are functionally the same)

[torn wolf]

wait so i have a doubt

can we use elif instead of else

cause im very confused on what situations do we use elif and else

[plain nimbus]

That would not make a lot of sense here.
elif is used if you want to check a 2nd condition. You would have to explain to me why you need that here.

If your number isn't even it is odd. There is no other possibility.

[torn wolf]

how is elif and if different than?

[torn wolf]

ohh yeah true

[plain nimbus]

else will execute regardless of your condition (but not if one of your previous if or elif statements executed)
You can imagine them like this

if condition:
    ...
elif condition2:
    ...
# is equal to
if condition:
    ...
else:
    if condition2:
        ...

[torn wolf]

so cant we just write another if statement instead of an elif

for another condition

?

[plain nimbus]

Yes you can, but then there is the possibility that both of them will run. You don't have that with if/elif - they are mutually exclusive

If both conditions in my example are True, then only the first if statement will run. With 2 individual ifs both of them will execute.

[torn wolf]

ohh

[plain nimbus]

Another way of saying it would be that two if statements are independent of another ||(while on the same level of indentation - nested ifs are obviously a different case)||, while an elif is always "connected" to an if statement.

[torn wolf]

ohh so like dependent on the if statmenet

[plain nimbus]

Yeah, elif will only check it's condition if the if statement failed it's own check.

Did you just add a melon to your name? xD

[torn wolf]

help yeah loll 😭

[torn wolf]

OHH

that makes sm sense now

[plain nimbus]

You can also have multiple elifs in a row, each of which will only check it's condition if the previous one failed

And if you have an else after those that will only run if all of the previous checks failed.

[torn wolf]

n=int(input("Enter value of N: "))
term=0
for i in range(1, n + 1):
    f = 1
    for j in range(1, i + 1):
        f = f * j
        if i % 2 == 0:
            term = (-(x ** i)) / f
        else:
            term = (+(x ** i)) / f
            result += term```

[rugged nimbus]

Hey @torn wolf!

It looks like you pasted Python code without syntax highlighting.

Please use syntax highlighting to improve the legibility of your code and make it easier for us to help you.

To do this, use the following method:
```py
print('Hello, world!')
```

This will result in the following:

print('Hello, world!')```
You can **edit your original message** to correct your code block.

[plain nimbus]

Ah almost!

[torn wolf]

ohh thank u sm elif always confused me

[torn wolf]

wait help what is left now 😭

[plain nimbus]

You made a small error regarding indentation

Where your loop that calcualtes the factorial expands to your if statement

You don't want that, since you want to finish calculating the factorial first before moving on.

Otherwise you will have an "unfinished" value in f

[torn wolf]

ohhh

[plain nimbus]

And the same thing (indentation) happens with your result (the term is only added to your result if your number is odd)

[torn wolf]

n=int(input("Enter value of N: "))
term=0
for i in range(1, n + 1):
    f = 1
    for j in range(1, i + 1):
        f = f * j
    if i % 2 == 0:
          term = (-(x ** i)) / f
    else:
          term = (+(x ** i)) / f
result += term```

[rugged nimbus]

Hey @torn wolf!

It looks like you pasted Python code without syntax highlighting.

Please use syntax highlighting to improve the legibility of your code and make it easier for us to help you.

To do this, use the following method:
```py
print('Hello, world!')
```

This will result in the following:

print('Hello, world!')```
You can **edit your original message** to correct your code block.

[torn wolf]

is it correct now?

[plain nimbus]

No 😦

You still need to add you term to your result for every... well term (in your 1st outer for loop)

    if i % 2 == 0:
          term = (-(x ** i)) / f
    else:
          term = (+(x ** i)) / f
# also you should indent 4 spaces after if/else
    if i % 2 == 0:
        term = (-(x ** i)) / f
    else:
        term = (+(x ** i)) / f```

[torn wolf]

help im so awful at indenation

that thing has been my biggest hater since i started python

[plain nimbus]

Yeah sorry, can't help you there - that's something you have to learn when writing python

It replaces {} in most other languages

[torn wolf]

x=float(input("Enter value of x: "))
n=int(input("Enter value of N: "))
term=0
result=0
for i in range(1, n + 1):
    f = 1
    for j in range(1, i + 1):
        f = f * j
    if i % 2 == 0:
          term = (-(x ** i)) / f
    else:
          term = (+(x ** i)) / f
result+=term
print(result)```

[torn wolf]

yeah i have been doing more problems, got way better compared to before 🙏

[plain nimbus]

x=float(input("Enter value of x: "))
n=int(input("Enter value of N: "))
result=0
for i in range(1, n + 1):
    f = 1
    for j in range(1, i + 1):
        f = f * j
    if i % 2 == 0:
          term = (-(x ** i)) / f
    else:
          term = (+(x ** i)) / f
    result += term
print(result)```
Since you're so close, this would be the correct indentation

[torn wolf]

ohhhh

[plain nimbus]

Also I removed the term=0 since it's not necessary here

[torn wolf]

OH IT HAS TO BE INSIDE THE FOR I LOOP 😭

[torn wolf]

oh yeahhh

n=int(input("Enter value of N: "))
result=0
for i in range(1, n + 1):
    f = 1
    for j in range(1, i + 1):
        f = f * j
    if i % 2 == 0:
          term = (-(x ** i)) / f
    else:
          term = (+(x ** i)) / f
    result += term
print(result)```

wait so this is final code right?

[rugged nimbus]

Hey @torn wolf!

It looks like you pasted Python code without syntax highlighting.

Please use syntax highlighting to improve the legibility of your code and make it easier for us to help you.

To do this, use the following method:
```py
print('Hello, world!')
```

This will result in the following:

print('Hello, world!')```
You can **edit your original message** to correct your code block.

[plain nimbus]

Yes, you want to save every term, not just the last one 😛

It produces the same results as my code, so I would say you're good yeah ^^

!e ```py
from math import factorial

def sum_of_series(n: int, x: float):
result = x
for i in range(2, n + 1):
if i % 2 == 0:
result -= xi / factorial(i)
else:
result += xi / factorial(i)

return result

def t(n, x):
result = 0
for i in range(1, n + 1):
f = 1
for j in range(1, i + 1):
f = f * j
if i % 2 == 0:
term = (-(x ** i)) / f
else:
term = (+(x ** i)) / f
result += term
return result

for b in range(5, 8):
for a in range(3, 7):
print(f"a:{a}, b:{b}, {sum_of_series(a, b)}, {t(a, b)}")

[rugged nimbus]

:white_check_mark: Your 3.12 eval job has completed with return code 0.

001 | a:3, b:5, 13.333333333333332, 13.333333333333332
002 | a:4, b:5, -12.708333333333336, -12.708333333333336
003 | a:5, b:5, 13.333333333333332, 13.333333333333332
004 | a:6, b:5, -8.368055555555557, -8.368055555555557
005 | a:3, b:6, 24.0, 24.0
006 | a:4, b:6, -30.0, -30.0
007 | a:5, b:6, 34.8, 34.8
008 | a:6, b:6, -30.0, -30.0
009 | a:3, b:7, 39.666666666666664, 39.666666666666664
010 | a:4, b:7, -60.37500000000001, -60.37500000000001
... (truncated - too many lines)

Full output: https://paste.pythondiscord.com/6SLQSV65RAWKIJI22DO7NYPU6M

[torn wolf]

ohh true true

[plain nimbus]

Good job 👍

[torn wolf]

omg thank u sm!! i know i was being a huge pain with the stupid doubts, not only u helped with my homework, u also cleared a lot of doubts

again thank u sm, u literally saved my life 😭

[plain nimbus]

You're welcome 😄

[torn wolf]

i hope u have a wonderful day!!!!

@serene mauve thank u for ur help too!!!

[plain nimbus]

You too

You can use !close to close this thread

[torn wolf]

thanks i was so confused loll

!close

[rugged nimbus]

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