Python从列表中删除空项目

Question

I created the following list in python for DynamoBIM :

a = [["f", "o", "c"], [null, "o", null], [null, "o", null]]

I want to remove the null items from this list to create this list:

a = [["f", "o", "c"], ["o"], ["o"]]

I've attempted list.remove(x) , filter s, for -loops, and a number of other methods but cannot seem to get rid of these buggers.

How can I do this?

Answer 1

Assuming you mean None by null, you can use a list comprehension:

>>> null = None
>>> nested_list = [["f", "o", "c"], [null, "o", null], [null, "o", null]]
>>> [[x for x in y if x] for y in nested_list]
[['f', 'o', 'c'], ['o'], ['o']]

In case null is some other value, you can alter the above to set the value of null as that something else, and alter the comprehension to:

>>> null = None # Replace with your other value
>>> [[x for x in y if x != null] for y in nested_list]
[['f', 'o', 'c'], ['o'], ['o']]

Answer 2

a = [["f", "o", "c"], [None, "o", None], [None, "o", None]]
l = []
for i in a:
    l.append(filter(lambda x: x is not None, i))

print (l)

[['f', 'o', 'c'], ['o'], ['o']]

Answer 3

Actually Null is not in python, their it should be string like

list_value = [["f", "o", "c"], ['null', "o", 'null'], ['null', "o", 'null']]

[filter(lambda x: x!='null' and x!=None, inner_list) for inner_list in list_value]

[['f', 'o', 'c'], ['o'], ['o']]

You could also solve by nested list comprehension:

[[for i in inner_list if i!='null' and not i] for inner_list in list_value]

Answer 4

Assuming you meant None , you could try using the filter() function:

a = [["f", "o", "c"], [None, "o", None], [None, "o", None]]
print [filter(None,x) for x in a] 

---

>>> 
[['f', 'o', 'c'], ['o'], ['o']]

Answer 5

You can use a simple list comprehension:

>>> a = [["f", "o", "c"], [None, "o", null], [null, "o", None]]
>>> a = [[sub for sub in item if sub] for item in a]
>>> a
[['f', 'o', 'c'], ['o'], ['o']]
>>> 

This is equivalent to:

a = [["f", "o", "c"], [None, "o", null], [null, "o", None]]
new = []
for item in a:
    _temp = []
    for sub in item:
        if sub:
            _temp.append(sub)
    new.append(_temp)

a = new

---

>>> a = [["f", "o", "c"], [None, "o", null], [null, "o", None]]
>>> new = []
>>> for item in a:
...     _temp = []
...     for sub in item:
...         if sub:
...             _temp.append(sub)
...     new.append(_temp)
... 
>>> a = new
>>> a
[['f', 'o', 'c'], ['o'], ['o']]
>>> 

Answer 6

There is a difference between "None" and NaN ("not a number") in Python, which is sometimes conventionally referred to as "null." The data type of NaN is generally a float. Therefore, if you are working with a list of only strings, as seems to be the case here, one idea is to filter for strings using a list comprehension.

a = ["f", "o", "c", np.nan]
b = [c for c in a if type(c)==str]