dict 遍历

• digits.keys()
• digits.values()
• digits.items()

digits={'one':1,
       'two':2,
       'three':3}

# 默认遍历 key
for k in digits:
   print(k)
for k in digits.keys():
   print(k)

# 遍历 value
for value in digits.values():
   print(value)

# 遍历 key/value
for key,value in digits.items():
   print(key,value)