python - 搜索函数python

Question

您好，我正在尝试在 Python 中创建一个搜索函数，它遍历一个列表并在其中搜索一个元素。

到目前为止我得到了

def search_func(list, x)

      if list < 0:
            return("failure")
      else:
            x = list[0]

      while x > list:
            x = list [0] + 1    <----  how would you tell python to go to the next element in the list ? 
      if (x = TargetValue):
          return "success"
      else 
          return "failure" 

Answer 1

嗯，您当前的代码不是很 Pythonic。而且有几个错误!您必须使用索引来访问列表中的元素，更正您的代码，如下所示:

def search_func(lst, x):
    if len(lst) <= 0:   # this is how you test if the list is empty
        return "failure"
    i = 0               # we'll use this as index to traverse the list
    while i < len(lst): # this is how you test to see if the index is valid
        if lst[i] == x: # this is how you check the current element
            return "success"
        i += 1          # this is how you advance to the next element
    else:               # this executes only if the loop didn't find the element
        return "failure" 

...但是请注意，在 Python 中您很少使用 while 来遍历列表，一种更自然和更简单的方法是使用 for，它会自动绑定(bind)一个每个元素的变量，而不必使用索引:

def search_func(lst, x):
    if not lst:    # shorter way to test if the list is empty
        return "failure"
    for e in lst:  # look how easy is to traverse the list!
        if e == x: # we no longer care about indexes
            return "success"
    else:
        return "failure" 

但我们可以甚至 Pythonic!您要实现的功能非常普遍，已经内置到列表中。只需使用 in 来测试元素是否在列表中:

def search_func(lst, x):
    if lst and x in lst: # test for emptiness and for membership
        return "success"
    else:
        return "failure"