如何使用python3替换列表中的元素？

Question

如何使用python3替换列表列表中的元素？

txt =[[""],[""],[""]]
for i in txt:
   x = i.replace("", "apples")
   print(x)

  

预期输出：

apples
apples
apples

Answer 1

要替换主列表""的子列表中txt的每个实例，可以使用以下列表理解：

txt =[[""],[""],[""]]
txt = [[x if not x=="" else 'apples' for x in sublist] for sublist in txt]

产生：

[['apples'], ['apples'], ['apples']]

---

您现在拥有的代码无法使用，因为给定您在txt上循环的方式，i是子列表，而python列表对象没有.replace方法。

Answer 2

def replace(value, new_value, outer_list):    
  for inner_list in outer_list:
    for i,element in enumerate(inner_list):
       if element == value:
          inner_list[i]= new_value
  return outer_list
txt =[[""],[""],[""]]
txt = replace("", "apple", txt)

此功能可以满足您的需求

Answer 3

尝试这个：

txt = [[""],[""],[""]]
for i in range(len(txt)):
    for ii in range(len(txt[i])):
        txt[i][ii] = (txt[i][ii]).replace("","apples")
print(txt)

Answer 4

使用列表理解：

txt =[[""],[""],[""]]

print([[x if x != "" else 'apples' for x in sub] for sub in txt])

输出：

[['apples'], ['apples'], ['apples']]

要分别打印；

txt = [[x if x != "" else 'apples' for x in sub] for sub in txt]

for sub in txt:
   for elem in sub:
      print(elem)

输出：

apples
apples
apples