要检查定义的变量是否为字符串类型，我们可以使用两个函数，它们是Python库函数，
使用 isinstance()
使用 type()
isinstance()函数接受两个参数– 1）变量名（对象）和 2）数据类型（类），并返回对象是类的实例还是其子类的实例。
语法：
isinstance(obj, class_or_tuple)
示例
# 变数
a = 100 # 整数变量
b = 10.23 # 浮点变量
c = 'A' # 一个字符变量
d = 'Hello' # 字符串变量
e = "Hello" # 字符串变量
# 检查类型
if isinstance(a, str):
print("Variable \'a\' is a type of string.")
else:
print("Variable \'a\' is not a type of string.")
if isinstance(b, str):
print("Variable \'b\' is a type of string.")
else:
print("Variable \'b\' is not a type of string.")
if isinstance(c, str):
print("Variable \'c\' is a type of string.")
else:
print("Variable \'c\' is not a type of string.")
if isinstance(d, str):
print("Variable \'d\' is a type of string.")
else:
print("Variable \'d\' is not a type of string.")
if isinstance(e, str):
print("Variable \'e\' is a type of string.")
else:
print("Variable \'e\' is not a type of string.")输出结果
Variable 'a' is not a type of string. Variable 'b' is not a type of string. Variable 'c' is a type of string. Variable 'd' is a type of string. Variable 'e' is a type of string.
type() 函数接受一个参数（其他参数是可选的），并返回其类型。
语法：
type(object)
示例
# 变数
a = 100 # 整数变量
b = 10.23 # 浮点变量
c = 'A' # 一个字符变量
d = 'Hello' # 字符串变量
e = "Hello" # 字符串变量
# 检查类型
if type(a) == str:
print("Variable \'a\' is a type of string.")
else:
print("Variable \'a\' is not a type of string.")
if type(b) == str:
print("Variable \'b\' is a type of string.")
else:
print("Variable \'b\' is not a type of string.")
if type(c) == str:
print("Variable \'c\' is a type of string.")
else:
print("Variable \'c\' is not a type of string.")
if type(d) == str:
print("Variable \'d\' is a type of string.")
else:
print("Variable \'d\' is not a type of string.")
if type(e) == str:
print("Variable \'e\' is a type of string.")
else:
print("Variable \'e\' is not a type of string.")输出结果
Variable 'a' is not a type of string. Variable 'b' is not a type of string. Variable 'c' is a type of string. Variable 'd' is a type of string. Variable 'e' is a type of string.