python3 中采用 in 方法
#判断字典中某个键是否存在
arr = {"int":"整数","float":"浮点","str":"字符串","list":"列表","tuple":"元组","dict":"字典","set":"集合"}
#使用 in 方法
if "int" in arr:
print("存在")
if "float" in arr.keys():
print("存在")
#判断键不存在
if "floats" not in arr:
print("不存在")
if "floats" not in arr:
print("不存在")
python 3中不支持 has_key()，python2 中支持
#判断字典中某个键是否存在
arr = {"int":"整数","float":"浮点","str":"字符串","list":"列表","tuple":"元组","dict":"字典","set":"集合"}
#使用自带的has_key()
if(arr.has_key("int")):
print("存在")
