我照着课程讲义打的第三个示例指定{}的名字w,c,b,i 的程序运行代码了一遍，报错信息如下
Traceback (most recent call last): File "index.py", line 7, in result = template.format(w = world, c = china, b = beijing, i = imoooc) NameError: name 'imoooc' is not defined
template = "Welcome to {w}, {c}, {b}, {i}"
world = "World"
china = "China"
beijing = "Beijing"
# 这里没有定义 imoooc 变量
result = template.format(w = world, c = china, b = beijing, i = imoooc)
print(result)