How to switch?

Question

Hello Pythoneers!
I am trying to write a program for ATM that accepts from user a choice of operation and executes an operation, which is basically a method. As we know there is no switch case in Python. SO how to handle it without it?
As piece of script you can find below:
https://code.sololearn.com/cWH9ofLI40Ze

Answer 1

# Simply chain 'if' and 'elif' (else if) statements:

if choice == 1:
print('choice 1')
elif choice == 2:
print('choice 2')
elif choice == 3:
print('choice 3')
elif choice == 4:
print('choice 4')

# or you can define a dict (or list in case of continuous numeric keys) containing function to execute:

def onchoice1():
print('choice 1')

def onchoice2():
print('choice 2')

def onchoice3():
print('choice 3')

def onchoice4():
print('choice 4')

choices = { 1: onchoice1, 2 : onchoice2, 3 : onchoice3, 4 : onchoice4 }

choices[choice]()

Answer 2

hello Saidamamad brother ! i am from tajikistan do you have viber or imo

Answer 3

I did this task using C# once, but I need to learn Python now. It is a little bit confusing for me (

Answer 4

# Lambda are useful to define short functions, so in such case as my examples, lambda are useful to avoid defining named function.

# On the other hand, in your last example lambdas are used only to define a call to another function: you could do better with:

return { 1 : ATM.checkBalance,
2: ATM.withdraw,
3: ATM.deposit,
4: ATM.exitProgram,
}.get(choice,ATM.errorOccured)()

Answer 5

Practice, practice and practice again is the key... with curiosity: at each new problem to solve, you will search solutions, reading stuff, discovering new language features, and so step by step you will get more ideas for next problems to solve ;)

Answer 6

Thank you very much!!! 🙏

Answer 7

@visph thanks a lot! That one works! I did similar to that but in dictionary I wrote the parantheses along with the method name, so when the program run, the methods in the dictionary are executed 😂 which is unwanted.

choices[choice] () is amazing trick! 😊👍

Answer 8

And I found a tutorial in youtube, which shows a good way also by defining a class method:

@classmethod
def operation(cls, choice):
return{ 1: lambda: ATM.checkBalance(),
2: lambda: ATM.withdraw(),
3: lambda: ATM.deposit(),
4: lambda: ATM.exitProgram(),
}.get(choice,lambda: ATM.errorOccured())()

while(True):
try:
choice = int(input('Operation mode: '))
except:
ATM.errorOccured()
continue;
ATM.operation(choice)

Answer 9

It use a temporary dict with lambda functions under the hood ;)

Use of lambda could be a good idea (depending on context), but use of temporary litteral dict is not really, even if the lack of efficiency doesn't have a real impact in almost contexts ^^

Answer 10

So using lambda should be avoided in this case? Didn't get you well :(

Answer 11

Thank you very much, @visph! I am very week for these kind of tricks :( I don't know how to get like these ideas for problem solving :)

Answer 12

it is corret