This question already has answers here:
Bitwise operation and usage
(17 answers)
Closed 7 months ago.
I have tried to find out about these operations in Python:
x|3
x^3
x>>=3
x<<=3
I couldn't find anything. Please can anyone tell me what are these operations are called, so that I can search more about them.
See: https://docs.python.org/3/reference/datamodel.html#emulating-numeric-types
Python has methods known as "magic" or "dunder" (i.e. double-under) methods like __add__() that define what happens when operators like + are used.
Related
This question already has answers here:
Why not python implicit line continuation on period?
(6 answers)
Closed 10 months ago.
I have never seen this repeated dot syntax, and I can't find any pointers to it anywhere.
Is it application of unsqueeze followed by expand followed by float() ?
input_mask_expanded = (attention_mask
.unsqueeze(-1)
.expand(token_embeddings.size())
.float())
It's equivalent to
input_mask_expanded = (attention_mask.unsqueeze(-1).expand(token_embeddings.size()).float())
Just in a more readable form
This question already has answers here:
Does Python support short-circuiting?
(3 answers)
Closed 5 years ago.
I have a question about a logical expression of the following sort:
for i in range (k): #k is large
if (a==b and test(c)==b): #test() takes some time to calculate
do something
Now I want to know, how the logical expression is processed. Are the two simple expressions calculated first and then combined via and? Or is a==b calculated, and in case it is False, test(c)==b neglected?
Thanks.
The a==b will be calculated first, and if it's true then the second expression will be evaluated. This is known as 'short-circuiting', see the docs.
This question already has answers here:
Check if a value exists in an array in Cython
(2 answers)
Closed 6 years ago.
In Python we could use if x in list: so I was wondering if there's a similar command in C, so that we don't have to go through the whole thing using a for.
How can you know whether a value is contained in an array without cycling through it? This is exactly what Python does under the hood. No, there's no magical way to instantly know this.
This question already has answers here:
What do square brackets, "[]", mean in function/class documentation?
(4 answers)
Closed 7 years ago.
I'm using python for a long time. but it was always strange to me why In python references, commands are written like this:
del var1[,var2[,var3[....,varN]]]]
I know that if I want to use the above command I should write it in this way:
del var1, var1
I can't understand the meaning of [] is it related to the lists? any help will be appreciated.
Its just showing that these parameters are optional. This is normal style for references.
There is nothing to do with this in python. Just a tutorial explanation.
I bealive, this is taken origin from Usage message
This question already has answers here:
How to test multiple variables for equality against a single value?
(31 answers)
Closed 7 years ago.
I have problems to set up correctly my if statement.
This is my code:
def task_13():
Main_meal=['Meat','Cheese','Fish']
addons=['Potatoes','Rice','Salad']
my_meal=[(x+y) for x in Main_meal for y in addons if (x+y)!= 'FishRice' and 'CheeseRice']
print(my_meal)
My question is why Python filter out the 'CheeseRice' when is it stated there but only filter out the 'FishRice' option.
This is my output:
['MeatPotatoes', 'MeatRice', 'MeatSalad', 'CheesePotatoes', 'CheeseRice', 'CheeseSalad', 'FishPotatoes', 'FishSalad']
Thank you for your advice.
Here's the official reference on Python operator precedence, note that and is lower precedence than !=, so the != is evaluated first. Also and is a simple operator that takes the booleans on either side and returns a boolean representing their logical AND, it doesn't do what you tried to make it do.
Instead of
if (x+y)!= 'FishRice' and 'CheeseRice'
you need:
if (x+y)!= 'FishRice' and (x+y) != 'CheeseRice'
or alternatively
if (x+y) not in ('FishRice', 'CheeseRice')