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pythonif-statementfor-loopdictionary
Christopher Rajendran
Christopher Rajendran

Reputation: 17

Python Using IF inside FOR loop

This question might be very silly but i am trying to use the dictionary to iterate and return the result. I know how to iterate over dictionary but i want to check if the entered key exists in the dictionary and i want the program to print if the value is present or not.

class companyx:

    def __init__(self,empid):

        self.empid=empid

    def employees(self):

        employees={1:'Jane',2:'David',3:'Chris',4:'Roger'}

        entered=self.empid

        for emp in employees :
            if emp == entered:
                print ('Hi '+employees[emp] +' you are an employee of companyx.com')
        print('You dont belong here')

emp=companyx(2)

emp.employees()

When i pass a parameter which is not in the dictionary, i want the function to print "You dont belong here"

Upvotes: 1

Views: 20264

Answers (6)

abarnert
abarnert

Reputation: 366133

The most pythonic way to do this is to just try the lookup, and handle failure if it happens:

try:
    print('Hi '+employees[entered] +' you are an employee of companyx.com')
except KeyError:
    print('You dont belong here')

There's no reason for the for loop; the whole point of dictionaries is that you can look things up in one step, d[key], instead of having to loop over the keys and check whether each one == key.

You could use in to check whether the key exists, and then look it up. But that's a little silly—you're looking up the key to see whether you can look up the key. Why not just look up the key?

You can do this by using the get method, which returns None (or you can pass a different default value) if the key is missing:

name = employees.get(entered)
if name:
    print('Hi '+name +' you are an employee of companyx.com')
else:
    print('You dont belong here')

But it's Easier to Ask Forgiveness than Permission. Besides being slightly more concise, using try and except makes it clear that finding the name is the normal case that should be true, and not finding it is the exceptional case.

Upvotes: 2

Óscar López
Óscar López

Reputation: 236150

The easiest (and most idiomatic) way to check if a key is in a dictionary is:

if entered in employees:

The above replaces the for/if part of your code. Notice that there's no need to explicitly traverse the dictionary, the in operator takes care of checking membership. Short and sweet :) The complete code would look like this:

def employees(self):
    employees = {1:'Jane', 2:'David', 3:'Chris', 4:'Roger'}
    if self.empid in employees:
        print('Hi ' + employees[self.empid] + ' you are an employee of companyx.com')
    else:
        print("You don't belong here")

Upvotes: 9

user2555451
user2555451

Reputation:

Use the in keyword to quickly perform dictionary lookups:

if entered in employees:
    # the key is in the dict
else:
    # the key could not be found

Upvotes: 3

yan
yan

Reputation: 20992

You don't need to iterate through the dictionary to do that. You can write:

def employees(self):

    employees={1:'Jane',2:'David',3:'Chris',4:'Roger'}
    employee = employees.get(self.empid)

    if employee:
        print ('Hi ' + employee + ' you are an employee of companyx.com')
    else:
        print ('You dont belong here')

Upvotes: 2

Aidan Kane
Aidan Kane

Reputation: 4006

No need for a for loop - you just need:

if entered in employees:
    print 'blah'
else:
    print 'You do not belong here'

Upvotes: 1

dbf
dbf

Reputation: 6499

Try this:

if entered in employees.keys():
    ....
else:
    ....

Upvotes: 2

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