How to convert ‘false’ to 0 and ‘true’ to 1 in Python

Question

Is there a way to convert true of type unicode to 1 and false of type unicode to 0 (in Python)?

For example: x == 'true' and type(x) == unicode

I want x = 1

PS: I don't want to use if - else .

Answer 1

Use int() on a boolean test:

x = int(x == 'true')

int() turns the boolean into 1 or 0 . Note that any value not equal to 'true' will result in 0 being returned.

Answer 2

If B is a Boolean array, write

B = B*1

(A bit code golfy.)

Answer 3

您可以使用x.astype('uint8')其中x是您的布尔数组。

Answer 4

Here's a yet another solution to your problem:

def to_bool(s):
    return 1 - sum(map(ord, s)) % 2
    # return 1 - sum(s.encode('ascii')) % 2  # Alternative for Python 3

It works because the sum of the ASCII codes of 'true' is 448 , which is even, while the sum of the ASCII codes of 'false' is 523 which is odd.

---

The funny thing about this solution is that its result is pretty random if the input is not one of 'true' or 'false' . Half of the time it will return 0 , and the other half 1 . The variant using encode will raise an encoding error if the input is not ASCII (thus increasing the undefined-ness of the behaviour).

---

Seriously, I believe the most readable, and faster , solution is to use an if :

def to_bool(s):
    return 1 if s == 'true' else 0

See some microbenchmarks:

In [14]: def most_readable(s):
    ...:     return 1 if s == 'true' else 0

In [15]: def int_cast(s):
    ...:     return int(s == 'true')

In [16]: def str2bool(s):
    ...:     try:
    ...:         return ['false', 'true'].index(s)
    ...:     except (ValueError, AttributeError):
    ...:         raise ValueError()

In [17]: def str2bool2(s):
    ...:     try:
    ...:         return ('false', 'true').index(s)
    ...:     except (ValueError, AttributeError):
    ...:         raise ValueError()

In [18]: def to_bool(s):
    ...:     return 1 - sum(s.encode('ascii')) % 2

In [19]: %timeit most_readable('true')
10000000 loops, best of 3: 112 ns per loop

In [20]: %timeit most_readable('false')
10000000 loops, best of 3: 109 ns per loop

In [21]: %timeit int_cast('true')
1000000 loops, best of 3: 259 ns per loop

In [22]: %timeit int_cast('false')
1000000 loops, best of 3: 262 ns per loop

In [23]: %timeit str2bool('true')
1000000 loops, best of 3: 343 ns per loop

In [24]: %timeit str2bool('false')
1000000 loops, best of 3: 325 ns per loop

In [25]: %timeit str2bool2('true')
1000000 loops, best of 3: 295 ns per loop

In [26]: %timeit str2bool2('false')
1000000 loops, best of 3: 277 ns per loop

In [27]: %timeit to_bool('true')
1000000 loops, best of 3: 607 ns per loop

In [28]: %timeit to_bool('false')
1000000 loops, best of 3: 612 ns per loop

Notice how the if solution is at least 2.5x times faster than all the other solutions. It does not make sense to put as a requirement to avoid using if s except if this is some kind of homework (in which case you shouldn't have asked this in the first place).

Answer 5

If you need a general purpose conversion from a string which per se is not a bool, you should better write a routine similar to the one depicted below. In keeping with the spirit of duck typing, I have not silently passed the error but converted it as appropriate for the current scenario.

>>> def str2bool(st):
try:
    return ['false', 'true'].index(st.lower())
except (ValueError, AttributeError):
    raise ValueError('no Valid Conversion Possible')


>>> str2bool('garbaze')

Traceback (most recent call last):
  File "<pyshell#106>", line 1, in <module>
    str2bool('garbaze')
  File "<pyshell#105>", line 5, in str2bool
    raise TypeError('no Valid COnversion Possible')
TypeError: no Valid Conversion Possible
>>> str2bool('false')
0
>>> str2bool('True')
1

Answer 6

Any of the following will work:

s = "true"

(s == 'true').real
1

(s == 'false').real
0

(s == 'true').conjugate()    
1

(s == '').conjugate()
0

(s == 'true').__int__()
1

(s == 'opal').__int__()    
0


def as_int(s):
    return (s == 'true').__int__()

>>>> as_int('false')
0
>>>> as_int('true')
1

Answer 7

+(False)转换为 0， +(True)转换为 1

Answer 8

bool to int: x = (x == 'true') + 0

Now the x contains 1 if x == 'true' else 0.

Note: x == 'true' will return bool which then will be typecasted to int having value (1 if bool value is True else 0) when added with 0.

Answer 9

You could also use strtobool :

In [1]: import distutils

In [2]: distutils.util.strtobool("false")
Out[2]: 0

In [3]: distutils.util.strtobool("true")
Out[3]: 1

Answer 10

only with this:

const a = true; const b = false;

console.log(+a);//1 console.log(+b);//0

Answer 11

I use:

>>> str(bool(0))
'False'

>>> str(bool(1))
'True'