又是Python初學者問題,關於空串列等等

Question

""我理解為空字串
[]為空串列
請問下面碼中的 args[0][:0]該理解為什麼呢
用type(args[0][:0])會顯示為<class 'list'>
請問它與[]有什麼不同及特性呢?
我將它替換為[]後 print(adder1(["a","b"],["c","d"]))還能執行成功
執行 print(adder1("god","damn","it"))就報錯了
不了解其中差異.....

def adder1(*args):
    if type(args[0])==type(0):
        sum = 0
    else:
        sum = args[0][:0]
    for arg in args:
        sum = sum + arg
    return sum

print(adder1("god","damn","it"))
print(adder1(["a","b"],["c","d"]))

Answer 1

你如果对计算过程详细分析，就会发现其中的差别。python可变参数*para会将参数组成tuple存储。因此，

adder1("god","damn","it") # 该函数执行，args = ("god","damn","it")
adder1(["a","b"],["c","d"]) # 该函数执行，args = (["a","b"],["c","d"])

python基础牢固的，都知道

# 对于args = ("god","damn","it")
args[0][:0] = ''
# 对于args = (["a","b"],["c","d"])
args[0][:0] = []

很明显是两种不同的类型，一种是''，空字符串；一种是[]空的list。python里面，字符串和list都可以直接
进行运算，所以有了上面的结果。