使用python根据变量正确打印字符

Question

I'd like to know if there was a good pythonic way to do something like this:

size1 = 4 
size2 = 3
value = size1 - size2

def isSign(value):
    if value > 0 :
        return "+"
    else :
        return ""

print("My total gain is" + isSign(value) + str(value))

In this case my string should look like this:

My total gain is +1

In a case where value is -1 my string should look like this:

My total gain is -1

In a case where value is 0 my string should look like this:

My total gain is 0

I'd also like to avoid extern modules if possible.

Answer 1

You can replace isSign(value) with (value > 0) * "+" .

This works because True == 1 and False == 0 , and a number n times a string is that string repeated n times, so 0 * "+" is the empty string "" .

However, some may find it unreadable, as evidenced by the fact that I have to explain how it works.

Using an f-string:

f"My total gain is {(value > 0) * '+'}{value}"

Answer 2

f字符串是执行此操作的好方法：

print(f'My total gain is {"+" if value > 0 else ""}{value}') 

Answer 3

String formatting provides a + flag for this:

>>> "{:+}".format(3)
'+3'
>>> "{:+}".format(-3)
'-3'