What Language is This?

Question

Going through some example code sent to me and honestly, I have no idea what language this is

def uniqify(arr):
     b = {}
     for i in arr:
         b[i] = 1
     return b.keys()

Is it Python?

I am also curious what keys() does. It's obvious it returns an array but what does it do the array that calls the function? :P

EDIT: You guys are awesome!

Answer 1

Type it in the python interpreter. If it runs, it is python.

Answer 2

Yes, it's Python. b.keys returns a list of all the keys in the dictionary b. Each item in the sequence arr becomes a key in b whose value is 1. Note that lists and tuples are typically used where arrays would be used in other languages.

Also note that arr can be any iterable object (list, tuple, set, dict, collection), which is sort of the essence of duck typing in Python.

Answer 3

Yes, those {} are the dictionary literal, they create an empty dictionary.

Then, it iterate the array receives as argument and create as key the value of each element in the array, and as value a 1 ( which is just a random value )

Later it returns the keys of the dictionary.

For a better understanding see the output:

$python
>>> def uniqify(arr):
...      b = {}
...      for i in arr:
...          b[i] = 1
...      return b.keys()
... 
>>> uniqify(["a","a","b", "c", "c", "a", "b", "c"])
['a', 'c', 'b']

Since the dictionary only accept one value as key, consecutive additions with the same key are discarded.

Answer 4

Yes, it's Python.

b is a dict (dictionary) which is a mapping of keys to values. b.keys() returns a list of keys.

However this code is rather old fashioned. set(arr) will return a set of the unique values in arr.

Answer 5

Yeah, this is python.

def uniqify(arr): #this line defines a python function with a parameter
     b = {} #declare a variable with type dictionary
     for i in arr: #loop the array and get all the elements 
         b[i] = 1 #set dict b[key,value] with key got from arr 
     return b.keys() #return all the keys, actually,just the arr

Answer 6

As Longpoke explained, it's python, using a dict get the unique items.

However, it's bad python.

list(set(arr))

Does the same thing. No need to re-invent the wheel.

Answer 7

Trying it out in the Python Interactive Shell and calling the function with a list of letters (alphabets). Added comments preceded by # for your understanding.

>>> def uniqify(arr):
         # b is an empty dictionary
...      b = {}
         # for each item (indicated by the name i) in arr
...      for i in arr:
             # in the dictionary b, the key of value i is assigned a value 1
...          b[i] = 1
         # return all the keys in the dictionary b
...      return b.keys()
...

# arr is a list of alphabets/letters
>>> arr = ['a','b','c','d','e']

# call uniqify function passing the list arr as the argument.
>>> uniqify(arr)

# the result is a list of all keys (which is same as arr)

['a', 'c', 'b', 'e', 'd']

Answer 8

It's ancient Python -- it would work fine in Python 1.5.2, final release February 2001 (and possibly earlier versions too). Still runs fine in the latest and greatest versions of course (both 2.7 and 3.1), but there are better ways these days (and there have been for years) -- many have already suggested sets, no doubt best, but even if you "need" to use dicts (e.g., you've made a bet;-),

def uniqify(arr):
  return dict.fromkeys(arr).keys()

will do exactly the same thing in a faster and much more compact way. dict.fromkeys means "make a dict with the following keys (and all identical values, by default None)" and its keys method works just like in your original example.