How can I print out something when I have KeyError for my dictionary in Python?

Question

So I have a code for my dictionary:

def get_rooms_for(dict1, num):
    try:
        for x in dict1:
            if x == num:
                print(dict1[x])
    except KeyError:
        print (num,"is not available.")       

And my test is

get_rooms_for({'CS101':3004, 'CS102':4501, 'CS103':6755,'NT110':1244, 'CM241':1411}, 'CS999')

And I expect my result is to print out 'num' parameter with string saying

CS999 is not available.

But when I put it this it returns empty What should i have to do if I want to pick an KeyError in dictionary, using exception code??

Answer 1

When you enter the try loop you're then looping over all the keys in the dictionary. CS999 isn't a key in the dictionary, so you never try to access it. Thus you never hit a KeyError , and the except clause is never reached.

What you want to do is more like this:

def get_rooms_for(dict1, num):

    if num in dict1:
        print(dict1[num])
    else:
        print("{} is not available".format(num))

But Python already has a method for that: get

dict1.get(num, "{} is not available".format(num))

Which will return the value mapped to num if it's in the dictionary, and "{} is not available".format(num) if it's not.

Answer 2

Try this :

def get_rooms_for(dict1, num):
    try:
        for x in dict1:
            if dict1[num] == x:
                print "It will print particular key's {0} value if its exists or It will generate keyerror".format(dict1[num])
            print(dict1[x])
    except KeyError:
        print (num,"is not available.")

Output :

('CS999', 'is not available.')

Answer 3

try this one :

def get_rooms_for(dict1, num):
    try:
       print(dict1[num])
    except KeyError:
       print (num,"is not available.")

Answer 4

You also can try without try and exception :

def get_rooms_for(dict1, num):
    if dict1.has_key(str(num)): # or str(num) in dict1
            print "Key available"
    else:
        print num,"is not available."

get_rooms_for({'CS101':3004, 'CS102':4501, 'CS103':6755,'NT110':1244, 'CM241':1411}, 'CS999') 

output:

CS999 is not available.