Is there a simple way to delete a list element by value?

2018-06-25 05:57:28

a=[1,2,3,4]
b=a.index(6)
del a[b]
print a

The above shows the following error:

Traceback (most recent call last):
  File "D:zjm_codea.py", line 6, in <module>
    b=a.index(6)
ValueError: list.index(x): x not in list

So I have to do this:

a=[1,2,3,4]
try:
    b=a.index(6)
    del a[b]
except:
    pass
print a

But is there not a simpler way to do this?

To remove an element's first occurrence in a list, simply use list.remove :

>>> a = ['a', 'b', 'c', 'd']
>>> a.remove('b')
>>> print a
['a', 'c', 'd']

Mind that it does not remove all occurrences of your element. Use a list comprehension for that.

>>> a = [10, 20, 30, 40, 20, 30, 40, 20, 70, 20]
>>> a = [x for x in a if x != 20]
>>> print a
[10, 30, 40, 30, 40, 70]

Usually Python will throw an Exception if you tell it to do something it can't so you'll have to do either:

if c in a:
    a.remove(c)

or:

try:
    a.remove(c)
except ValueError:
    pass

An Exception isn't necessarily a bad thing as long as it's one you're expecting and handle properly.

You can do

a=[1,2,3,4]
if 6 in a:
    a.remove(6)

but above need to search 6 in list a 2 times, so try except would be faster

try:
    a.remove(6)
except:
    pass

链接地址: http://www.djcxy.com/p/70688.html