October 08, 2021    /    Viewed: 134    /    Comments: 0    /    Edit

Examples of how to get the sign of a number (e.g -1 or +1) in python:

### Get the sign of a number in python

Let's consider the following variables in python:

````x1 = 42`

`x2 = -24`
```

To get the sign of those numbers a solution is to use the function copysign(x, y) from python's math module:

````import math`

`math.copysign(1,x1)`
```

will returns:

````1`
```

while

````math.copysign(1,x2)`
```

will returns:

````-1`
```

copysign(a,b) gives the sign of b and the absolute value of a, So for example:

````math.copysign(-4,2)`
```

gives

````4`
```

### Create a sign function from math.copysign(1, x)

Create a function sign

````sign = lambda x: math.copysign(1, x)`
```

then

````x = 42`

`sign(x)`
```

gives

````1`
```

Another example

````x = -24`

`sign(x)`
```

gives

````-1`
```

Another example, try to create your own function

````def mysign(x):`
`    if x >= 0: `
`        return 1`
`    else:`
`        return -1`
```

Then

````x = 42`
`print( mysign(x) )`
```

gives

````1`
```

while

````x = -24`
`print( mysign(x) )`
```

gives

````-1`
```  ##### Daidalos

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