将列表的空字符串转换为浮点数

Question

I have a list of strings like this:

grades = [['2.0', '3.67', '3.67', '2.33', '3.67', '2.0', '3.67', '2.33', '3.0', '2.33', '', '3.67', '2.33', '2.67', '3.0', '2.0', '4.0', '3.33', '4.0'],[...]]

and it contains grades but it also has empty items. When I convert it to float it deletes those empty.

What I do is the following:

def try_convert(val):
    try:
        return float(val)
    except ValueError as TypeError:
        pass

floatGrades = [[float(z) for z in (try_convert(j) for j in i) if z] for i in grades]

Is there a way of turning the empty strings like this into 0?or None?

Answer 1

I would prefer using the function only to check if is possible or not. With that you would be able to make the function more generic; for general use:

grades = [['2.0', '3.67', '3.67', '2.33', '3.67', '2.0', '3.67', '2.33', '3.0', '2.33', '', '3.67', '2.33', '2.67', '3.0', '2.0', '4.0', '3.33', '4.0']]

def try_convert(val):
    try:
        float(val)
        return True
    except ValueError:
        return False

# Get only values that can convert to float
result = [float(x) for values in grades for x in values if try_convert(x) == True]
# When can convert float(value) else None
result = [float(x) if try_convert(x) == True else None for values in grades for x in values ]