Python - Synonyms and Antonyms

from nltk.corpus import wordnet

synonyms = []

for syn in wordnet.synsets("Soil"):
    for lm in syn.lemmas():
             synonyms.append(lm.name())
print (set(synonyms))

set([grease', filth', dirt', begrime', soil', 
grime', land', bemire', dirty', grunge', 
stain', territory', colly', ground'])

from nltk.corpus import wordnet
antonyms = []

for syn in wordnet.synsets("ahead"):
    for lm in syn.lemmas():
        if lm.antonyms():
            antonyms.append(lm.antonyms()[0].name())

print(set(antonyms))

set([backward', back'])