By "strip" I don't mean strip for each item, I mean remove items, for instance, 

```
a = [None, "a", "b", "c", None, None, None]
b = ["4", "4", "a", "b", "c", "4", "4"]
c = ["4", "4", "a", "4", "b", "c", "4", "4"]

```

what I want to keep is

```
["a", "b", "c"] # for the first two
["a", "4", "b", "c"] # for the last one

```

by such a method or function, 

```
a.strip(None)  # or strip(a, None)   
b.strip("4")  # or strip(b, "4")

```

I think I can do it using a for loop with a flag to detect the two ends, but I thought it may be not pythonic.