3. enumerate

enumerate is an iterable object that provides an extremely useful technique to create a dictionary from a list whose keys are the list indexes. One of the ways this can be helpful is when you use matplotlib to plot, where in the xticks correspond to numbers, but the label (that appears on the X-axis) needs to be the 2 character State Code.

>>> State = ['AK', 'AL', 'AR', 'AZ', 'CA', 'CO', 'CT', 'DC', 'DE', 'FL', 'GA', 'HI',
       'IA', 'ID', 'IL', 'IN', 'KS', 'KY', 'LA', 'MA', 'MD', 'ME', 'MI', 'MN',
       'MO', 'MS', 'MT', 'NC', 'ND', 'NE', 'NH', 'NJ', 'NM', 'NV', 'NY', 'OH',
       'OK', 'OR', 'PA', 'RI', 'SC', 'SD', 'TN', 'TX', 'UT', 'VA', 'VT', 'WA',
       'WI', 'WV', 'WY']
>>> T = dict(enumerate(State))
>>> T
{0: 'AK', 1: 'AL', 2: 'AR', 3: 'AZ', 4: 'CA', 5: 'CO', 6: 'CT', 7: 'DC', 8: 'DE', 9: 'FL', 10: 'GA', 11: 'HI', 12: 'IA',
 13: 'ID', 14: 'IL', 15: 'IN', 16: 'KS', 17: 'KY', 18: 'LA', 19: 'MA', 20: 'MD', 21: 'ME', 22: 'MI', 23: 'MN', 24: 'MO',
 25: 'MS', 26: 'MT', 27: 'NC', 28: 'ND', 29: 'NE', 30: 'NH', 31: 'NJ', 32: 'NM', 33: 'NV', 34: 'NY', 35: 'OH', 36: 'OK',
 37: 'OR', 38: 'PA', 39: 'RI', 40: 'SC', 41: 'SD', 42: 'TN', 43: 'TX', 44: 'UT', 45: 'VA', 46: 'VT', 47: 'WA', 48: 'WI',
 49: 'WV', 50: 'WY'}