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The tilde operator in Python
(9 answers)
Closed 1 year ago.
pd_selftest = pd_selftest[pd_selftest['SICCD'] != 0]
pd_selftest = pd_selftest[~pd_selftest['SICCD'].isnull()]
I'd like to know what the function of the ~ is in the above code.
That's the bit-wise invert or not operator. So, it returns only those lines where the SICCID column is not null. I would probably use the word not in this case.
Related
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Real world use cases of bitwise operators [closed]
(41 answers)
Bitwise operation and usage
(17 answers)
Closed 12 months ago.
I understand that the bitwise and operator (&) is equivalent to a product of two bit values. When would I use it?
Please also help me understand what num&1 does in the code below:
def func(num):
n = 1 + func((3*num+1) if num&1 else (num>>1))
return n
As the comments mentioned, num&1 is a bitwise AND between num and 1.
Since 1 in binary is ...000000001, the AND will result True iff the least significant bit of num is 1, in other words, if it is odd (here some explanation of binary)
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Why is exponentiation applied right to left?
(4 answers)
Closed 2 years ago.
print (2**3**2)
Answer is 512.
Why 512 is answer not 64? Because ((2^3)^2) = 64
I want to know the inside math operation of print (2** 3**2)
The order of operations for exponentiation is right-to-left, not-left-to right. So:
2**3**2
is interpretted as:
2**(3**2) = 2**(9) = 512
This question already has answers here:
numpy matrix vector multiplication [duplicate]
(1 answer)
What does the "at" (#) symbol do in Python?
(14 answers)
Closed 3 years ago.
I am trying to understand some code in which I found this statement. I don't know what "#" sign is doing here.
This is a running code for landmark detection, you can check full code here: https://github.com/cleardusk/3DDFA/blob/master/utils/ddfa.py
vertex = p # (u + w_shp # alpha_shp + w_exp # alpha_exp).reshape(3, -1, order='F') + offset
I believe it's used for matrix multiplication. Refer this for more: What does the "at" (#) symbol do in Python?
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Math operations from string [duplicate]
(8 answers)
Closed 6 years ago.
I have a string with a formula 5 - 3, and I need to get the result in integer. How could I do that?
use eval function:
eval("5 - 3") # 2
test = "5-3"
print(eval(test))
Gives 2
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Python ? (conditional/ternary) operator for assignments [duplicate]
(2 answers)
Closed 7 years ago.
I Java it's possible to represent IF-THEN statement in the following form:
a = (x==10) ? true : false;
that is equivalent to
if (x==10)
a=true;
else
a=false;
Is it possible to do the same thing in Python?
a = True if x == 10 else False
or simply
a = x == 10