Flipping the boolean values in a list Python
PythonPython Problem Overview
I have a boolean list in Python
mylist = [True , True, False,...]
which I want to change to the logical opposite [False, False, True , ...]
Is there an inbuilt way to do this in Python (something like a call not(mylist) ) without a hand-written loop to reverse the elements?
Python Solutions
Solution 1 - Python
It's easy with list comprehension:
mylist = [True , True, False]
[not elem for elem in mylist]
yields
[False, False, True]
Solution 2 - Python
The unary tilde operator (~) will do this for a numpy.ndarray. So:
>>> import numpy
>>> mylist = [True, True, False]
>>> ~numpy.array(mylist)
array([False, False, True], dtype=bool)
>>> list(~numpy.array(mylist))
[False, False, True]
Note that the elements of the flipped list will be of type numpy.bool_ not bool.
Solution 3 - Python
>>> import operator
>>> mylist = [True , True, False]
>>> map(operator.not_, mylist)
[False, False, True]
Solution 4 - Python
Numpy includes this functionality explicitly. The function "numpy.logical_not(x[, out])" computes the truth value of NOT x element-wise.
import numpy
numpy.logical_not(mylist)
http://docs.scipy.org/doc/numpy-1.10.0/reference/generated/numpy.logical_not.html (with same examples)
Example:
import numpy
mylist = [True , True, False]
print (mylist)
returns [True, True, False]
mylist=numpy.logical_not(mylist)
print (mylist)
returns [False False True]
Solution 5 - Python
numpy.invert is another nice option:
x = [False, True, True]
not_x = np.invert(x) # [True, False, False]
Solution 6 - Python
Why not just use a simple list comprehension?
mylist[:] = [not x for x in mylist]
Solution 7 - Python
I would do it the way everybody else is saying, but for sake of documenting alternatives, you could also do
import operator
myList = map(operator.not_, myList)
Solution 8 - Python
what about the following
>>> import numpy
>>> list(numpy.asarray(mylist)==False)