🔒 I made a simple calculator but can i improve?(i am new to python)

[opal bough]

This the my code
first_value = float(input("First: "))
second_value = float(input("Second: "))
action = input("Action:(+,-,,/) ")
if action == "+" :
Sum = float(first_value) + float(second_value)
print("Answer:", Sum)
elif action == "-" :
subtract = float(first_value) - float(second_value)
print("Answer:", subtract)
elif action == "" :
multiply = (float(first_value) * float(second_value))
print("Answer:", multiply)
elif action == "/" :
divide = (int(first_value) / int(second_value))
print("Answer:", divide)

[chrome hound]

@opal bough

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[visual walrus]

This first thing I would do is add a final else: to catch an unexpected action value.

[opal bough]

i have done it

wait

[visual walrus]

You don't need to call float() in the calculations because you already did that with the inputs.

[opal bough]

first_value = float(input("First: "))
second_value = float(input("Second: "))
action = input("Action:(+,-,,/) ")
if action == "+" :
Sum = float(first_value) + float(second_value)
print("Answer:", Sum)
elif action == "-" :
subtract = float(first_value) - float(second_value)
print("Answer:", subtract)
elif action == "" :
multiply = (float(first_value) * float(second_value))
print("Answer:", multiply)
elif action == "/" :
divide = (int(first_value) / int(second_value))
print("Answer:", divide)
print("Please use +,-,*,/ for it to work :) ")

[visual walrus]

... no else: ?

[unreal urchin]

if you know context free grammars, regex and at least functions you could write a parser

[opal bough]

yeah

[opal bough]

lets just say i started learning like an hour ago

and i am a engineering student

so no idea about coding

i find it fun

thats why i wanna learn it

[flat phoenix]

One thing you can do is have a variable result, and then no matter what branch you take on the if statements you can later print("ANSWER: "+result), without having to do it for each operation

[opal bough]

sorry i didnt get it

so like remove every line from the if statements?

[unreal urchin]

i mean for a better calulator you could use eval or better ast.literal_eval but i think that is not what you want because you want to code it yourself and not just use a built-in function?

[opal bough]

i am just messing around

only posted it for tips

altho i would love to know what is eval and '''ast.literal_eval'''

[flat phoenix]

Like, instead of having

if x:
    something = ...
    print("ANSWER: "+something)
if y:
    something = ...
    print("ANSWER: "+something)
...```
you can have
```py
if x:
    result = ...
if y:
    result = ...

print("ANSWER: "+result)```

[unreal urchin]

ast is a module (it stands for abstract syntax tree) and the function literal_eval from this module treats a given string as an python literal and evaluates it and returns the result

[opal bough]

ahhhhhh but then if i use the wrong thing in Action: it wouldnt tell me that i messed up

forexample my last string is

else :print("Please use +,-,*,/ for it to work :) ")

[unreal urchin]

and eval treats a string as one python expression and evaluates (and executes) it and returns the result

[opal bough]

could u please use it on my code to like give an example?

[flat phoenix]

Yeah, that's true. If you used elif it could work though, maybe try that next :)

[opal bough]

my code has 3 elif XD

[flat phoenix]

Oh true

Then it'll work

No wait

[opal bough]

hm?

[flat phoenix]

I'm dumb hang on

[opal bough]

ok ok

tyt

[flat phoenix]

You could check if the input is valid (i.e the else block didn't run) with a boolean flag. Then, only if it's valid, you print result

is_valid = True
if condition_1:
     ...
elif condition_2:
    ...
elif condition_3:
    ...
else:
     is_valid = False

if is_valid:
     print("Answer: "+result)```

[opal bough]

i dont know what is a boolean flag

is it the true and false thingy?

[flat phoenix]

Yeah!

[flat phoenix]

Do you get the gist of this?

[opal bough]

no tbh

[unreal urchin]

inp = input("enter a calculation task: ")
print(f"the result is: {eval(inp)}")

but this is not good, you would have to use regex to check if the input is only a calulation task. and i was wrong you can not use ast.literal_eval for something like: "5 + 7 * 9 - 2 ** 4" or "1 + 2" because it is an expression and not a literal

[flat phoenix]

Ok, let me get a concrete example

is_tasty= True
food = input()
if food == "Pizza":
     ingredients = "flour, cheese"
elif food == "Tacos":
    ingredients= "eggs, flour"
elif food == "steak":
    ingredients= "meat"
else: #If we reach this else we know the food isn't tasty, since the only tasty foods are pizza, tacos and steak
     print("Your food isn't tasty!")
     is_tasty = False

if is_tasty: #If we reached the else clause this will be False, and so we won't print the ingredients 
     print("Ingredients: "+ingredients)```

One website I recommend when starting out is pythontutor.com, there you can see for yourself which steps your code takes, in an interactive way, which can really help you reason about the logic of your program

[blazing arch]

I'd recommend doing the CS50 Python course from harvard, it is free online, high quality and there is a discord community where you can get help with the coding exercises if you need, it will give you a good solid base with python

[chrome hound]

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