merging in python

Question

Hi all

I have the following 4 arrays ( grouped in 2 groups ) that I would like to merge in ascending order by the keys array.

I can use also dictionaries as structure if it is easier.

Has python any command or something to make this quickly possible?

Regards MN

# group 1
[7, 2, 3,  5]  #keys
[10,11,12,26]  #values 

[0,   4]   #keys
[20,  33]  #values 

# I would like to have
[ 0, 2, 3, 4, 5, 7 ] # ordered keys
[20, 11,12,33,26,33] # associated values

Answer 1

I would recommend that you use dictionaries, then you can use d.update to update one dictionary with keys and values from the other.

Note that dictionaries in Python are not ordered. Instead when you need to iterate you can get their keys, order those and iterate over the keys in order getting the corresponding values.

If you are using Python 2.7, or 3.1 or better then there is a class OrderedDict that you might want to use.

Answer 2

Look at zip in combination with dictionary if your keys are guaranteed to be unique.

You just do:

>>> x = [7, 2, 3,  5]  #keys
>>> y = [10,11,12,26]  #values 

>>> dict(zip(x,y))
{2: 11, 3: 12, 5: 26, 7: 10}

Answer 3

1. Add all keys and associated values from both sets of data to a single dictionary.
2. Get the items of the dictionary ans sort them.

3. print out the answer.

   k1=[7, 2, 3, 5] v1=[10,11,12,26]

   k2=[0, 4] v2=[20, 33]

   d=dict(zip(k1,v1)) d.update(zip(k2,v2))

   answer=d.items() answer.sort() keys=[k for (k,v) in answer] values=[v for (k,v) in answer]

   print keys print values

Edit: This is for Python 2.6 or below which do not have any ordered dictionary.

Answer 4

If your keys are not guaranteed to be unique you should not use a dictionary - duplicate keys will be overwritten.

This solution works for duplicate keys:

keys_a = [7, 2, 3,  5]
values_a = [10,11,12,26]
keys_b = [0,   4]
values_b = [20,  33]

combined = zip(keys_a+keys_b, values_a+values_b)
combined.sort()

keys, values = zip(*combined)

(Edited to use @tgray's suggested improvement)