I was wondering if it was possible to do the following:
very_special = ["special"]
my_list = ["stuff", very_special]
if "special" in my_list:
print ("Found it")
I was wondering if you could do this in some way, having the code look through the whole thing, including the lists inside the list.
You can achieve this by using recursion. Something along these lines:
very_special = ["special"]
my_list = ["stuff", very_special]
def nested_list_search(lst, term):
for ele in lst:
if isinstance(ele, list):
nested_list_search(ele, term)
else:
if ele == term:
print("Found it")
nested_list_search(my_list, "special")
>>> Found it
Other user here suggested recursion...It might be an overkill for what he asked for. You can just look over items as well.
very_special = ["special"]
my_list = ["stuff", very_special]
if "special" in my_list:
print("Found it")
for item in my_list:
if isinstance(item, list) and "special" in item:
print("Found it nested inside")
If the nesting is only one level deep, you can loop over each element in the outer list:
for elem in my_list:
if elem == "special" or (isinstance(elem, collections.Iterable) and "special" in elem):
print("Found it.")
If you want to handle arbitrary nesting, you'll need to flatten them first (like Flatten (an irregular) list of lists):
def flatten(lst):
for elem in lst:
if isinstance(elem, collections.Iterable) and not isinstance(elem, (str, bytes)):
yield from flatten(elem)
else:
yield elem
if "special" in flatten(my_list):
print ("Found it")
For this situation you need some work around, Here is a snippet to achieve it. Same way you can write your own to work on.
very_special = ["special", "v", ["xyz", "we"]]
my_list = ["stuff", "n", very_special]
def aggregate(newList):
opList = []
for item in newList:
if list is type(item):
opList += aggregate(item)
else:
opList.append(item)
return opList
if "special" in aggregate(my_list):
print ("Found it")
Using the original suggestion way will not work. The membership operator in usually behavior is to check if x is member of y without going deeper to check if x is also member of any member of y.
For this case, for this specific example, here is a very specific way to solve this.
very_special = ["special"]
my_list = ["stuff", very_special]
for element in my_list:
if "special" in element:
print ("Found it")
Depending on your needs, the following approach might be appropriate:
import itertools
very_special = ["special"]
my_list = ["stuff", very_special]
if "special" in itertools.chain.from_iterable(my_list):
print ("Found it")
This makes use of Python's chain() function which gets chained inputs from a single iterable argument that is evaluated lazily.
Using the + operator
very_special = ["special"]
my_list = ["stuff"] + very_special
if "special" in my_list:
print ("Found it")
