为什么 Python 说我不能将字符串转换为整数，因为它有空字符串？

Question

I'm making a procedure that takes in two coordinates as input, then calculating the midpoint. However, when I try to change the input into an integer after just taking the part of the coordinate with the x and y values, it says ValueError: invalid literal for int() with base 10: '' <--That's an empty string by the way. Here's my code:

def distance():
    p1=input('Input your first point:')
    p2=input('Input your second point:')
    split1=p1.find(',')
    x1=int(p1[2:split1-1])
    y1=p1[split1+1:-2]
    split2=p2.find(',')
    x2=p2[0:split2-1]
    y2=p2[split2+1:-1]
    x=x2-x1**2
    y=y2-y1**2
    d=(x+y)**.5
    print('This is the distance between those points',d)`

Answer 1

As others have said, int('') will yield this error because there is not a general consensus on what number '' should be converted to.

If you actually want a default value, consider using the following (where you want it to default to 0).

value = ''
intvalue = int(value or '0')

# 0

value = '1'
intvalue = int(value or '0')

# 1

That being said, an easier way to accomplish splitting the coordinates like you want would be to use split()

x,y = map(int, '1,2'.split(','))

If your input is actually of the form: (1, 2) , you will want to ignore the parentheses and only grab the numeric parts.

import re

val = '(1, 2)'
val = re.sub('\(|\)', '', val);
x,y = map(int, val.split(','))

Or more generically

val = '(-1, 2)' # or [-1, 2] or -1,2

val = re.search('\-?\d+\s*,\s*\-?\d+', val).group()
x,y = map(int, val.split(','))

For your specific example:

def getxy(val):
    val = re.search('\-?\d+\s*,\s*\-?\d+', val)

    # Alert the user if invalid input was provided
    if val is None:
        raise Exception('Invalid input')

    # Convert all coordinates to integers
    return map(int, val.group().split(','))

x1, y1 = getxy(input('Input your first point:'))
x2, y2 = getxy(input('Input your second point:'))

Answer 2

I think you want to use something likesplit() instead of fancing indexing to parse your input:

def distance():
    p1=input('Input your first point:')
    p2=input('Input your second point:')
    x1, y1 = p1.split(',', 1)
    x1 = int(x1)
    y1 = int(y1)
    x2, y2 = p2.split(',', 1)
    x2 = int(x2)
    y2 = int(y2)
    x=x2-x1**2
    y=y2-y1**2
    d=(x+y)**.5
    print('This is the distance between those points',d)`

Answer 3

You are ignoring the first two characters of your point, so if the number has only two digits, you get an empty string. Better split the string with split :

p1 = '(1,4)'
x1, y1 = p1[1:-1].split(',')
x1 = int(x1)

Answer 4

I got it, I'm still not entirely sure what I did wrong, but I added a comma split clause. In the beginning, I used replace like I did here, but it didn't work. This time, it did! Thanks to everyone who tried to help. Here's my solution:

def distance():
p1=input('Input your first point:')
p2=input('Input your second point:')
rp1=p1.replace('(','').replace(')','')
x1, y1 = rp1.split(',', 1)
x1 = int(x1)
y1 = int(y1)
rp2=p2.replace('(','').replace(')','')
x2, y2 = rp2.split(',', 1)
x2 = int(x2)
y2 = int(y2)
x=(x2-x1)**2
y=(y2-y1)**2
d=(x+y)**.5
print('This is the distance between those points',d)