python可以定义变量先不赋值吗

variable_name = variable_value

x = 20                      # 声明整数类型变量

y = 40                      # 声明整数类型变量

s = "I love python"     # 声明字符串类型变量

flag = True                 # 声明布尔类型变量

u = 30.4                    # 声明浮点类型变量

print(flag)                 # 输出flag变量的值

print(x + y)                # 输出x和y的和

print(s)                    # 输出s变量的值

print(u)                    # 输出u变量的值

In [1]: name

---------------------------------------------------------------------------

NameError                                 Traceback (most recent call last)

<ipython-input-1-9bc0cb2ed6de> in <module>

----> 1 name

NameError: name 'name' is not defined

In [2]:

In [1]: name

---------------------------------------------------------------------------

NameError                                 Traceback (most recent call last)

<ipython-input-1-9bc0cb2ed6de> in <module>

----> 1 name

NameError: name 'name' is not defined

In [2]: name = 'Lucy'

In [3]: name

Out[3]: 'Lucy'

In [4]