Easy Python Question regarding Dictionaries

[M4rotku]

Hello all,

I am currently trying to write a phone book program just for the sake of gaining some experience. I would like to use a dictionary to keep track of the names and numbers before outputting them to a file. I have a loop set up that prompts the user for a name and its number over and over again. Is there any way in which I can use a function similar to what append() does for lists to add new definitions to my dictionary? The dictionary idea is as follows:


book = {name : number, name : number, etc}

If anyone can tell me of an append() equivalent function for dictionaries, it would be much appreciated.

Much thanks,
M4rotku

[Flimm]

dict = {}
dict["new name"] = 123456

Yup, you can assign values to new keys directly. Every key is unique, so assigning a value to an already existing key:value pair will overwrite the old value.

[M4rotku]

Thanks, I was a bit worried that I wouldn't be able to use a dictionary and thus wouldn't be able to sort the names and number.

Thanks for your quick response.

[M4rotku]

Okay, I ran into another problem with my dictionary. I need to be able to separate the keys from the values. This can be done with the .keys(), but I need to be able to do it one at a time.

For example, if my phonebook dictionary is defined as:


phonebook = {'home' : 123-456-7890, 'work' = 908-65-4321}

then I need a command that will allow me to extract 'home' so that i can print it to a file and then another command that will extract 123-456-7890 so that i can put that in a file. I'm guessing that the function would probably work so that I can specify the number of the key or value that I am extracting.

Ex)
phonebook.function(0) would return 'home'
phonebook.function(1) would return 'work'

Is there anything that does this? I would imagine that such a function has to exist.

Much thanks,
M4rotku

[sujoy]

phonebook = {'home' : "123-456-7890", 'work' : "908-65-4321"}
for key in phonebook.keys():
print "key is %s : value is %s" % (key,phonebook[key])

[M4rotku]

wow, can you explain what all of those % are doing? I've seen them in code before, but I have no idea what they are there for. I guess that works, but I was just looking for something a bit less confusing.

Can you put that in layman's terms?

[.Maleficus.]

%s is a string, so what you're doing is replacing every instance of "%s" in the preceding line with the respective value in the tuple following the % sign. SOOO...

The first instance of "%s" is replaced by the first value in (key,phonebook[key]). That is the value of the 'key' variable. The second instance is replaced by 'phonebook[key]'. This can go on an indefinite amount of times, ie, "%s %s %s" % (key, bookmark[key], var_x) would print the values of key, then bookmark[key], then var_x, if that makes sense.

[wmcbrine]

phonebook.function(0) would return 'home'
phonebook.function(1) would return 'work'

Is there anything that does this? I would imagine that such a function has to exist.No. A Python dictionary is unordered, by definition; it makes no sense to look for the Nth entry. Instead you must use .keys(), and parse the list it returns.

phonekeys = phonebook.keys()
phonekeys[0] # 'home'
phonekeys[1] # 'work'

Since there is no guaranteed order (and the order will change as you add items), you may also want to sort the list of keys.

[benj1]

why don't you use a nested dictionary or a list of dictionaries eg


mum = { home : '012345',mobile: '123456'}
dad = { home : '712345',mobile: '234567'}

then either:

phonebook = { entry1 : mum, entry2 : dad}

or


phonebook = [mum, dad]

then you can easily access all the details of one person or all home phone numbers etc

[Can+~]

why don't you use a nested dictionary or a list of dictionaries eg


mum = { home : '012345',mobile: '123456'}
dad = { home : '712345',mobile: '234567'}

then either:

phonebook = { entry1 : mum, entry2 : dad}

or


phonebook = [mum, dad]

then you can easily access all the details of one person or all home phone numbers etc

Or better, mum and dad are instances of a single class called Person, that has a home phone number, mobile phone number, ID, etc.