CODEWITHSUNDEEP
pythonlistdictionaryboolean
user3062260
user3062260

Reputation: 1644

building a boolean dictionary from 2 lists in python

I'm trying to make a dictionary with values 'True' or 'False' when comparing elements in 2 lists. This is probably a bit basic but I'm new to coding and I don't understand why it always assigns the 'True' value even though I can see its not true:

 letters = [A,B,C,D,E,F,G,H,I,J,K,L,M,N,O,P,Q,R,S,T,U,V,W,X,Y,Z]

 randomData = []

 f = open('randomData.txt', 'r')
 for line in f:
      randomData.append(line.rstrip().split()[0])
 f.close()

The 'randomData.txt' file looks like:

 A'\t'0003'\t'0025'\t'chr1
 B'\t'0011'\t'0021'\t'chr7
 D'\t'0043'\t'0068'\t'chr3
 F'\t'0101'\t'0119'\t'chr7

The randomData list should now look like:

 ['A','B','D','F']

I tried:

 sameLetters = {}

 i=0
 while i < len(letters):
     if letters[i] and randomData:
         #append to dictionary
         sameLetters[letters[i]] = 'True'
     else:
         #append to dictionary
         sameLetters[letters[i]] = 'False'
     i=i+1

 print sameLetters

I expected something like:

 {'A': 'True', 'B': 'True', 'C': 'False', 'D': 'True', 'E': 'False', 'F': 'True', 'G': 'False', etc

Instead all values in the dictionary are 'True'. Can anyone see the problem? Or give any pointers or explanations? Any help would be great, many thanks.

Upvotes: 1

Views: 271

Answers (3)

shengy
shengy

Reputation: 9749

Seems like you only care about which letter appears in your random data, so why not use a set?

from string import ascii_uppercase

randomData = ['A', 'B', 'D', 'F', 'A']

appeared = set(ascii_uppercase).intersection(set(randomData))
print appeared

And later you can us it like this:

char = 'z'
if char in appeared:
    print 'yes'
else:
    print 'no'

EDIT:

Then how about this:)

from string import ascii_uppercase

randomData = ['A', 'B', 'D', 'F', 'A']

appeared = set(ascii_uppercase).intersection(set(randomData))

d = dict(zip(ascii_uppercase, (False,) * 26))

for key in appeared:
    d[key] = True

print d

Upvotes: 0

jonrsharpe
jonrsharpe

Reputation: 122115

I think you want to do something like:

sameLetters = {l: l in randomData for l in letters}

Your current attempt doesn't work because you check

if letters[i] and randomData:
            # ^ should be in

and Python interprets both non-empty strings (letters[i]) and non-empty lists (randomData) as True.

Also, note that letters is already available in Python:

from string import ascii_uppercase

This is a string, but you can iterate through and index a string just like a list, and in will still work.

Upvotes: 1

C.B.
C.B.

Reputation: 8346

Perhaps you meant if letters[i] in randomData

Upvotes: 4

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