Compute BLEU Score for Machine Translation

compute-bleu.py

import sacrebleu
from sacremoses import MosesDetokenizer
md = MosesDetokenizer(lang='en')


# Open the test dataset human translation file and detokenize the references
refs = []

with open("target.test") as test:
    for line in test: 
        line = line.strip().split() 
        line = md.detokenize(line) 
        refs.append(line)
    
print("Reference 1st sentence:", refs[0])

refs = [refs]  # Yes, it is a list of list(s) as required by sacreBLEU


# Open the translation file by the NMT model and detokenize the predictions
preds = []

with open("target.pred") as pred:  
    for line in pred: 
        line = line.strip().split() 
        line = md.detokenize(line) 
        preds.append(line)

print("MTed 1st sentence:", preds[0])    


# Calculate and print the BLEU score
bleu = sacrebleu.corpus_bleu(preds, refs)
print(bleu.score)