L1 = ['Hello', 'World', 18, 'Apple', None]
L2 = []
for i in L1:
if isinstance(i, str) == True:
L2.append(i.lower())
L3 = [x.lower() for x in L1 if isinstance(x, str) == True]
# 测试:
print(L2)
print('****************')
print(L3)
if L3 == ['hello', 'world', 'apple']:
print('测试通过!')
else:
print('测试失败!')
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来一杯82年的咖啡不加糖
L1 = ['Hello', 'World', 18, 'Apple', None]
L2 = []
for i in L1:
if isinstance(i, str) == True:
L2.append(i.lower())
L3 = [x.lower() for x in L1 if isinstance(x, str) == True]
# 测试:
print(L2)
print('****************')
print(L3)
if L3 == ['hello', 'world', 'apple']:
print('测试通过!')
else:
print('测试失败!')