原始代码:
def make_great(magicians):
for magician in magicians:
magician = "the Great " + magician
print(magician)
return(magician)
magicians=['dante','vergil','leo']
make_great(magicians)
print(magicians)
运行结果:
the Great dante
the Great vergil
the Great leo
['dante', 'vergil', 'leo']
[Finished in 0.0s]
发现magicians这个列表并没有被修改。
Why?
我修改了一下代码。
修改代码:
def make_great(magicians):
n=len(magicians)
for i in range(0,n):
magicians[i]="The Great "+magicians[i]
print(magicians[i])
return magicians
magicians=['dante','vergil','leo']
make_great(magicians)
print(magicians)
运行结果:
The Great dante
The Great vergil
The Great leo
['The Great dante', 'The Great vergil', 'The Great leo']
[Finished in 0.1s]
成功了。
WHY?
推测:在原始代码中的for循环里的magician,并不能反向索引列表。所以,执行原始代码块时,只是magician这个临时变量被赋值,列表本身并没有影响。而在修改代码中,代码magicians[i]已经很明确地索引了列表第i-1位置的元素,所以这个修改是直接对该元素生效的。
刚自学Python,谬误之处请指正。