Problems with Dictionaries

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Problems with Dictionaries

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#1 by (3 votes)
#2 by (2 votes)

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I am trying to use a diccionario as a switch , My code is:

a = {'1': f1(x, y), '2':  f2(x)}
while True:
    try:
        selection = getOption()
        b = a[selection]

        break

    except Exception:
        print "Error"

But I have the following problem: If I select option 1, function f2 is executed, but this should not happen. How do I fix it?

python ciclos

asked by Alice 13.03.2016 в 18:47

source

2 answers

How to unify two tables into one? I can not convert from int to string to java

score 3 · Answer 1

The key of the dictionaries must be a String , so if getOption() returns an integer, you must parse it to a String .

a = {'1': f1(x, y), '2':  f2(x)}
while True:
    try:
        selection = getOption()
        b = a[str(selection)]

        break

    except Exception:
        print "Error"

score 2 · Answer 2

At the time of the dictionary definition, you are invoking the functions f1 and f2 , and the values returned are those that are inserted in the dictionary.

If you want a switch , one way would be:

funcs = { '1': f1, '2':f2 }
while True:
    selection = getOption()
    f = funcs.get(selection, None)
    if not f is None:
      f(x,y)
    else:
      print "No existe la función"

Problems:

All functions have to use the same number of arguments, even if they do not use all the arguments

All functions return some value

Error control grows as the number of switch cases increases, so it is best done within each function.

Of course, each of these problems can be avoided, but my recommendation is that you use structures if..elif..else and avoid spreading errors to other parts if you can (eg: getOption should control their own errors)

seleccion = getOption()
if seleccion == 1:
    f1(x,y)
elif seleccion == 2:
    f2(x)
else:
    print "Selección errónea"