Python - Dictionary With Default Values

defaultdict.py

hashmap = {
  'vegetables': ['Carrot', 'Tomato'],
  'fruits': ['Apple', 'Banana']
}

# **************
# Default Values
# **************

hashmap['missing_key'] # KeyError
hashmap.get('missing_key') # None
hashmap.get('missing_key', 'default value') # default value


# Get value or default value + append

# all of these are wrongs
hashmap['meat'].append('chicken') # Same case as line 10
hashmap.get('meat').append('chicken') # Same case as line 11
hashmap.get('meat', []).append('chicken') # Does not mutate hashmap, use setdefault instead

# This works
hashmap.setdefault('meat', []).append('chicken') # {.. 'meat': ['chicken']}


# **************
# With default dict
# **************

hashmap_default = defaultdict(list)
hashmap_default['vegetables'] = ['Carrot', 'Tomato']
hashmap_default['fruits'] = ['Apple', 'Banana']

hashmap['missing_key'] # [] as it is the default we specified when doing defaultdict(list)
hashmap.get('missing_key') # Still None!

hashmap['meat'].append('chicken') # {.. 'meat': ['chicken']}