Swapping 1 with 0 and 0 with 1 in a Pythonic way
PythonPython Problem Overview
In some part of my Python program I have a val variable that can be 1 or 0. If it's 1 I must change to 0, if it's 0 I must change to 1.
How do you do it in a Pythonic way?
if val == 1:
val = 0
elif val == 0:
val = 1
it's too long!
I did:
swap = {0: 1, 1:0}
So I can use it:
swap[val]
Other ideas?
Python Solutions
Solution 1 - Python
This isn't pythonic, but it is language neutral. Often val = 1 - val is simplest.
Solution 2 - Python
The shortest approach is using the bitwise operator XOR.
If you want val to be reassigned:
val ^= 1
If you do not want val to be reassigned:
val ^ 1
Solution 3 - Python
Since True == 1 and False == 0 in python,
you could just use var = not var
It will just swap it.
Solution 4 - Python
Just another possibility:
i = (1,0)[i]
This works well as long as i is positive, as dbr pointed out in the comments it doesn't work for i < 0.
Are you sure you don't want to use False and True? It sounds almost like it.
Solution 5 - Python
In your case I recommend the ternary:
val = 0 if val else 1
If you had 2 variables to swap you could say:
(a, b) = (b, a)
Solution 6 - Python
To expand upon the answer by "YOU", use:
int(not(val))
Examples:
>>> val = 0
>>> int(not(val))
1
>>> val = 1
>>> int(not(val))
0
Note that this answer is only meant to be descriptive, not prescriptive.
Solution 7 - Python
Here's a simple way:
val = val + 1 - val * 2
For Example:
If val is 0
0+1-0*2=1
If val is 1
1+1-1*2=0
Solution 8 - Python
If you want to be short:
f = lambda val: 0 if val else 1
Then:
>>> f(0)
1
>>> f(1)
0
Solution 9 - Python
The most pythonic way would probably be
int(not val)
But a shorter way would be
-~-val
Solution 10 - Python
I have swapped 0s and 1s in a list.
Here's my list:
list1 = [1,0,0,1,0]
list1 = [i^1 for i in list1]
#xor each element is the list
print(list1)
So the outcome is: [0,1,1,0,1]
Solution 11 - Python
Just another way:
val = ~val + 2
Solution 12 - Python
(0,1)[not val] flips the val from 0 to 1 and vice versa.
Solution 13 - Python
After seeing all these simpler answers i thought of adding an abstract one , it's Pythonic though :
val = set(range(0,2)).symmetric_difference(set(range(0 + val, val + 1))).pop()
All we do is return the difference of 2 sets namely [0, 1] and [val] where val is either 0 or 1.
we use symmetric_difference() to create the set [0, 1] - [val] and pop() to assign that value to variable val.
Solution 14 - Python
Another option:
val = (not val) * 1
Solution 15 - Python
Function with mutable argument. Calling the swaper() will return different value every time.
def swaper(x=[1]):
x[0] ^= 1
return x[0]
Solution 16 - Python
Your way works well!
What about:
val = abs(val - 1)
short and simple!
Solution 17 - Python
use np.where
ex.
np.where(np.array(val)==0,1,0)
this gives 1 where val is 0 and gives 0 where val is anything else, in your case 1
EDIT: val has to be array