给列表中每个元素加入标号

#给列表中每个元素加入标号

import datetime as dt
import matplotlib.pyplot as plt
from matplotlib import style
import pandas as pd
#import pandas_datareader.data as web

a = ['Mary', 'had', 'a', 'little', 'lamb']
for i in range(len(a)):
    print(i ,  '.' ,a[i])