Python 2.7 - Two lists as dictionary

Question

dict1 = open('dict1.txt','r')
dict2 = open('dict2.txt','r')

keys = []
values = []

for w in dict1:
   keys.append(w.strip())
   for key in keys:
       key


for x in dict2:
    values.append(x.strip())
    for val in values:
       val

dictionary = {key: val}

Text files contain 140 lines of single words. 'keys' is a list of words from the first file, 'values' is a list of words from the second file.

Whenever I print the dictionary, I get only the first pair. How to loop it inside dictionary so I get all 140 pairs?

I've tried doing this:

dictionary = {}
val = dictionary[key]

But I get 'KeyError' on the console. I know this is basic stuff but I've been struggling with it.

Answer 1

You can easily build the dictionary using zip :

for w in dict1:
   keys.append(w.strip())

for x in dict2:
    values.append(x.strip())

dictionary = dict(zip(keys, values))

Your KeyError is due to the assignment being the wrong way around:

val = dictionary[key]

tries to assign what is currently in dictionary for the key (which is nothing) to val . Instead, it should be:

dictionary[key] = val 

Your looping code is incorrect too:

for w in dict1:
   keys.append(w.strip())
   for key in keys: # looping over all keys so far each time
       key # doesn't do anything

And your first attempt:

dictionary = {key: val}

would create a new dictionary each time.

Answer 2

Use zip() to combine the keys and values from the two files. You can produce the whole dictionary in one go with just two lines of code:

with open('dict1.txt','r') as keys, open('dict2.txt','r') as values:
    dictionary = {key.strip(): value.strip() for key, value in zip(keys, values)}

Your code loops over the two files and after each loop, key and value are bound still to the last value of each iteration.