I have 2 Dictionaries:
StatePops={'AL':4887871, 'AK':737438, 'AZ':7278717, 'AR':3013825}
StateNames={'AL':'Alabama', 'AK':'Alaska', 'AZ':'Arizona', 'AR':'Arkansas'}
I am trying to merge so the Value of StateNames is the Key for StatePops.
Ex.
{'Alabama': 4887871, 'Alaska': 737438, ...
I also have to display the name of states w/ population over 4million.
Any help is appreciated!!!
You have not specified in what programming language you want this problem to be solved.
Nonetheless, here is a solution in Python.
state_pops = {
'AL': 4887871,
'AK': 737438,
'AZ':7278717,
'AR':3013825
}
state_names = {
'AL':'Alabama',
'AK':'Alaska',
'AZ':'Arizona',
'AR':'Arkansas'
}
states = dict([([state_names[k],state_pops[k]]) for k in state_pops])
final = {k:v for k, v in states.items() if v > 4000000}
print(states)
print(final)
First, you can merge two dictionaries with the predefined dict python function in the states variable as such. Here, k is an iterator and it is used as index for state_names and state_pops.
Then, store the filtered dictionary in final where the states.items() is used to access the keys and values in states and type-cast it as a string with the str function.
There may be more simpler solutions but this is as far as I can optimize the problem.
Hope this helps.
Dictionary Keys cannot be changed in Python. You need to either add the modified key-value pair to the dictionary and then delete the old key, or you can create a new dictionary. I'd opt for the second option, i.e., creating a new dictionary.
myDict = {}
for i in StatePops:
myDict.update({StateNames[i] : StatePops[i]})
This outputs myDict as
{'Alabama': 4887871, 'Alaska': 737438, 'Arizona': 7278717, 'Arkansas': 3013825}
Related
Having some trouble understanding how to create a Perl hash from a DB select statement.
$sth=$dbh->prepare(qq{select authorid,titleid,title,pubyear from books});
$sth->execute() or die DBI->errstr;
while(#records=$sth->fetchrow_array()) {
%Books = (%Books,AuthorID=> $records[0]);
%Books = (%Books,TitleID=> $records[1]);
%Books = (%Books,Title=> $records[2]);
%Books = (%Books,PubYear=> $records[3]);
print qq{$records[0]\n}
print qq{\t$records[1]\n};
print qq{\t$records[2]\n};
print qq{\t$records[3]\n};
}
$sth->finish();
while(($key,$value) = each(%Books)) {
print qq{$key --> $value\n};
}
The print statements work in the first while loop, but I only get the last result in the second key,value loop.
What am I doing wrong here. I'm sure it's something simple. Many thanks.
OP needs better specify the question and do some reading on DBI module.
DBI module has a call for fetchall_hashref perhaps OP could put it to some use.
In the shown code an assignment of a record to a hash with the same keys overwrites the previous one, row after row, and the last one remains. Instead, they should be accumulated in a suitable data structure.
Since there are a fair number of rows (351 we are told) one option is a top-level array, with hashrefs for each book
my #all_books;
while (my #records = $sth->fetchrow_array()) {
my %book;
#book{qw(AuthorID TitleID Title PubYear)} = #records;
push #all_books, \%book;
}
Now we have an array of books, each indexed by the four parameters.
This uses a hash slice to assign multiple key-value pairs to a hash.
Another option is a top-level hash with keys for the four book-related parameters, each having for a value an arrayref with entries from all records
my %books;
while (my #records = $sth->fetchrow_array()) {
push #{$books{AuthorID}}, $records[0];
push #{$books{TitleID}}, $records[1];
...
}
Now one can go through authors/titles/etc, and readily recover the other parameters for each.
Adding some checks is always a good idea when reading from a database.
I am still learning about python and I face some trouble extracting data from a dict. I need to create a loop which check each values and extract the keys. So for this code I need to find the nice students. I am stuck at line 3 #blank.
How do i go about this?
Thanks in advance
class = {"James":"naughty", "Lisa":"nice", "Bryan":"nice"}
for student in class:
if #blank:
print("Hello, "+student+" students!")
else:
print("odd")
Uses dictionary methods "keys(), values(), items()":
def get_students_by_criteria(student_class, criteria):
students = []
for candidate, value in student_class.items():
if value == criteria:
students.append(candidate)
return students
my_class = {"James":"naughty", "Lisa":"nice", "Bryan":"nice"}
print(get_students_by_criteria(my_class, "nice"))
Warning to the word "class" it is a keyword reserved for python programming oriented object
I have a dictionary of phone numbers where number is Key and country is value. I want to update the key and add country code based on value country. I tried to use the map function for this:
print('**Exmaple: Update phone book to add Country code using map function** ')
user=[{'952-201-3787':'US'},{'952-201-5984':'US'},{'9871299':'BD'},{'01632 960513':'UK'}]
#A function that takes a dictionary as arg, not list. List is the outer part
def add_Country_Code(aDict):
for k,v in aDict.items():
if(v == 'US'):
aDict[( '1+'+k)]=aDict.pop(k)
if(v == 'UK'):
aDict[( '044+'+k)]=aDict.pop(k)
if (v == 'BD'):
aDict[('001+'+k)] =aDict.pop(k)
return aDict
new_user=list(map(add_Country_Code,user))
print(new_user)
This works partially when I run, output below :
[{'1+952-201-3787': 'US'}, {'1+1+1+952-201-5984': 'US'}, {'001+9871299': 'BD'}, {'044+01632 960513': 'UK'}]
Notice the 2nd US number has 2 additional 1s'. What is causing that?How to fix? Thanks a lot.
Issue
You are mutating a dict while iterating it. Don't do this. The Pythonic convention would be:
Make a new_dict = {}
While iterating the input a_dict, assign new items to new_dict.
Return the new_dict
IOW, create new things, rather than change old things - likely the source of your woes.
Some notes
Use lowercase with underscores when defining variable names (see PEP 8).
Lookup values rather than change the input dict, e.g. a_dict[k] vs. a_dict.pop(k)
Indent the correct number of spaces (see PEP 8)
I am writing some code where I have multiple dictionaries for my data. The reason being, I have multiple core objects and multiple smaller assets and the user must be able to choose a smaller asset and have some function off in the distance run the code with the parent noted.
An example of one of the dictionaries: (I'm working in ROBLOX Lua 5.1 but the syntax for the problem should be identical)
local data = {
character = workspace.Stores.NPCs.Thom,
name = "Thom", npcId = 9,
npcDialog = workspace.Stores.NPCs.Thom.Dialog
}
local items = {
item1 = {
model = workspace.Stores.Items.Item1.Main,
npcName = "Thom",
}
}
This is my function:
local function function1(item)
if not items[item] and data[items[item[npcName]]] then return false end
end
As you can see, I try to index the dictionary using a key from another dictionary. Usually this is no problem.
local thisIsAVariable = item[item1[npcName]]
but the method I use above tries to index the data dictionary for data that is in the items dictionary.
Without a ton of local variables and clutter, is there a way to do this? I had an idea to wrap the conflicting dictionary reference in a tostring() function to separate them - would that work?
Thank you.
As I see it, your issue is that:
data[items[item[npcName]]]
is looking for data[“Thom”] ... but you do not have such a key in the data table. You have a “name” key that has a “Thom” value. You could reverse the name key and value in the data table. “Thom” = name
I am fairly new to Scalding and I am trying to write a scalding program that takes as input 2 datasets:
1) book_id_title: ('id,'title): contains the mapping between book ID and book title, Both are strings.
2) book_sim: ('id1, 'id2, 'sim): contains the similarity between pairs of books, identified by their IDs.
The goal of the scalding program is to replace each (id1, id2) in book_ratings with their respective titles by looking up the book_id_title table. However, I am not able to retrieve the title. I would appreciate it if someone could help with the getTitle() function below.
My scalding code is as follows:
// read in the mapping between book id and title from a csv file
val book_id_title =
Csv(book_file, fields=book_format)
.read
.project('id,'title)
// read in the similarity data from a csv file and map the ids to the titles
// by calling getTitle function
val result =
book_sim
.map(('id1, 'id2)->('title1, 'title2)) {
pair:(String,String)=> (getTitle(pair._1), getTitle(pair._2))
}
.write(out)
// function that searches for the id and retrieves the title
def getTitle(search_id: String) = {
val btitle =
book_id_title
.filter('id){id:String => id == search_id} // extract row matching the id
.project('title) // get the title
}
thanks
Hadoop is a batch processing system and there is no way to lookup data by index. Instead, you need to join book_id_title and book_sim by id, probably two times: for left and right ids. Something like:
book_sim.joinWithSmaller('id1->id, book_id_title).joinWithSmaller('id2->id, book_id_title)
I am not very familiar with the field-based API so consider the above as a pseudocode. You also need to add appropriate projections. Hopefully, it still gives you an idea.