How do I append the value of a key in a python dictionary?

Question

Okay so I have a program I'm writing in python, and it contains a dictionary. The dictiionary as of now looks like:

phoneList = {'Tom':'564-0000','Sue':'564-0000','Roberto':'564-0000'}

How would I go about adding the same area code to each of the key values. As of now this is what I've com up with, but I can't seem to get it to do what I want.

import copy

def main():

    phoneList = {'Tom':'564-0000','Sue':'564-0000','Roberto':'564-0000'}

    newDict = newDictWithAreaCodes(phoneList)
    #print(newDict)



def newDictWithAreaCodes(phoneBook):

    updatedDict = copy.copy(phoneBook)
    newStr = "518-"
    keyList = phoneBook.keys()   

    for key in keyList:

        del updatedDict[key]
        newKey = newStr + key
        updatedDict[key] = newKey


    print(updatedDict) 

Answer 1

Pretty straightforward with a comprehension:

{k:'{}-{}'.format(518,v) for k,v in phoneList.items()}
Out[56]: {'Roberto': '518-564-0000', 'Sue': '518-564-0000', 'Tom': '518-564-0000'}

And if I were to write that as a function:

def prepend_area_code(d, code = 518):
    '''Takes input dict *d* and prepends the area code to every value'''
    return {k:'{}-{}'.format(code,v) for k,v in d.items()}

Random comments:

• your phoneList is a dict , don't call it a list .
• also, follow python naming conventions for variables: phone_list , methods: new_dict_with_area_codes , etc.

Answer 2

Is this what you are looking for?

area_code = '567'

phoneList = {'Tom':'564-0000','Sue':'564-0000','Roberto':'564-0000'}

phoneList = {k : '-'.join((area_code, v)) for k, v in phoneList.iteritems()}

Result:

>>> phoneList
{'Sue': '567-564-0000', 'Roberto': '567-564-0000', 'Tom': '567-564-0000'}

Answer 3

I think you are confused with dictionary keys and values. Doing phoneBook.keys() gives you a list of keys in your phoneBook dictionary namely Tom, Roberto and Sue . phoneBook[key] gives the corresponding values.

I think you mean to concatenate '518' to the values of the keys? Your code concatenates the key to the value. You change this line in your code:

newKey = newStr + key

to:

newKey = newStr + phoneBook[key]

This will give you what you want, when you print updatedDict :

{'Sue': '518-564-0000', 'Roberto': '518-564-0000', 'Tom': '518-564-0000'}

---

You can achieve the same using dictionary comprehension like this:

>>> phoneList = {'Tom':'564-0000','Sue':'564-0000','Roberto':'564-0000'}
>>> newDict = {k: '518-' + v for k, v in phoneList.items()}
>>> newDict
{'Sue': '518-564-0000', 'Roberto': '518-564-0000', 'Tom': '518-564-0000'}

Answer 4

phoneList = {'Tom':'564-0000','Sue':'564-0000','Roberto':'564-0000'}

for key in phoneList:
    phoneList[key] = '518-' + phoneList[key]

produces:

{'Roberto': '518-564-0000', 'Sue': '518-564-0000', 'Tom': '518-564-0000'}