Python：从列表中删除不可转换为int的项的干净高效方法

Question

I have a list like this:

mylist = [1.0,2.0,3.0,4.0,...,u'*52', u'14*', u'16*',"", "" ,"",...]

It basically contains, float , unicodes and blank(string?) . (It could have other data types as well)

My objective is to remove any item which are not convertible to integer from the list.

I have tried using .isdigit() like this:

newlist= [i for i in mylist if i.isdigit()]

but I ended up having AttributeError :

AttributeError: 'float' object has no attribute 'isdigit'

What would be a clean and neat way (without using too many if/else or try/except clauses) to achieve this?

I am using python 2.7

Answer 1

You could use a helper function:

def convertible(v):
    try:
        int(v)
        return True
    except (TypeError, ValueError):
        return False

newlist = [i for i in mylist if convertible(i)]

Answer 2

from numbers import Number

mylist = [1.0,2.0,3.0,4.0,u'*52', u'14*', u'16*',"", "" ,""]

mylist[:] = [ele for ele in mylist if isinstance(ele,Number)]

print(mylist)

Why you get the AttributeError: 'float' object has no attribute 'isdigit' is because isdigit is a str method, you are trying to call it on an actual float.

mylist[:] changes the original list which may or may not be what you want, if you want to keep both just use newlist= ... .

Answer 3

For Your example list this can apply, "without using too many if/else or try/except clauses"

>>>[i for i in mylist if isinstance(i, (int, float))]
[1.0, 2.0, 3.0, 4.0]

Answer 4

Try the following code:

mylist = [1.0,2.0,3.0,4.0,u'*52', u'14*', u'16*']
newlst=[]
for i in mylist:
    try:
        newlst.append(int(i))
    except ValueError:

        pass
print newlst