numpy fromstring deprecated use frombuffer instead

Question

In the Python code using numpy 1.18.1

` def printBoard(self): current = self.player other = self.player % 2 + 1

    currBin   = '{:049b}'.format(self.current_position)
    currRev = currBin[::-1]

    cArr = (np.fromstring(currRev,'u1') - ord('0'))*current

    other_position = self.current_position^self.mask
    othBin   = '{:049b}'.format(other_position)
    othRev = othBin[::-1]

    oArr = (np.fromstring(othRev,'u1') - ord('0'))*other

    tArr =  oArr+cArr

    brd = np.reshape(tArr,(7,7),order = 'F')
    for y in range(bitBoard.HEIGHT,-1,-1):
        for x in range(bitBoard.WIDTH):
            print(brd[y,x],end = ' ')
        print()
    print()
    `

the line :

cArr = (np.fromstring(currRev,'u1') - ord('0'))*current

gives the following warning:

DeprecationWarning: The binary mode of fromstring is deprecated, as it behaves surprisingly on    unicode inputs. Use frombuffer instead
  cArr = (np.fromstring(currRev,'u1') - ord('0'))*current

Replacing 'fromstring' with 'frombuffer' gives the following error :

cArr = (np.frombuffer(currRev,'u1') - ord('0'))*current

TypeError: a bytes-like object is required, not 'str'

Despite some Googling I cannot find what I should use instead. Can anybody help?

Thank you.

Alan

Explain what those lines do conceptually. Your example is not minimal, and 90% of the code you posted is irrelevant to the problem. — Mad Physicist
– Mad Physicist, Commented Feb 20, 2020 at 13:30
I know I have given too much but often when I ask a question I get requested for the whole code! This time I gave the function hoping that would suffice. The lines take a column of a connect4 column encoded in binary form and convert it to 0 and 1 or 0 and 2 depending on the player. it adds the resulting arrays together and outputs the positions of the pieces in that column — Alan Johnstone
– Alan Johnstone, Commented Feb 20, 2020 at 15:26

hpaulj · Accepted Answer · 2020-02-20 17:07:34Z

7

The relevant part of your code is that which produces currRev. From that I can construct this example:

In [751]: astr = '{:049b}'.format(123)[::-1]                                                   
In [752]: astr                                                                                 
Out[752]: '1101111000000000000000000000000000000000000000000'

your warning:

In [753]: np.fromstring(astr, 'u1')                                                            
/usr/local/bin/ipython3:1: DeprecationWarning: The binary mode of fromstring is deprecated, as it behaves surprisingly on unicode inputs. Use frombuffer instead
  #!/usr/bin/python3
Out[753]: 
array([49, 49, 48, 49, 49, 49, 49, 48, 48, 48, 48, 48, 48, 48, 48, 48, 48,
       48, 48, 48, 48, 48, 48, 48, 48, 48, 48, 48, 48, 48, 48, 48, 48, 48,
       48, 48, 48, 48, 48, 48, 48, 48, 48, 48, 48, 48, 48, 48, 48],
      dtype=uint8)

frombuffer wants a bytestring, so let's create one:

In [754]: astr.encode()                                                                        
Out[754]: b'1101111000000000000000000000000000000000000000000'
In [755]: np.frombuffer(astr.encode(),'u1')                                                    
Out[755]: 
array([49, 49, 48, 49, 49, 49, 49, 48, 48, 48, 48, 48, 48, 48, 48, 48, 48,
       48, 48, 48, 48, 48, 48, 48, 48, 48, 48, 48, 48, 48, 48, 48, 48, 48,
       48, 48, 48, 48, 48, 48, 48, 48, 48, 48, 48, 48, 48, 48, 48],
      dtype=uint8)

And the rest of the line:

In [756]: _-ord('0')                                                                           
Out[756]: 
array([1, 1, 0, 1, 1, 1, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
       0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
       0, 0, 0, 0, 0], dtype=uint8)

Another way to get the same array:

In [758]: np.array(list(astr),'uint8')                                                         
Out[758]: 
array([1, 1, 0, 1, 1, 1, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
       0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
       0, 0, 0, 0, 0], dtype=uint8)

answered Feb 20, 2020 at 17:07

hpaulj

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3 Comments

Alan Johnstone Over a year ago

Thank you very much. That worked. I do not play with bits very much so I was unsure what to do.

hpaulj Over a year ago

In py2, default strings were byte size. In py3 unicode is the default, and bytestrings are marked with the b'...'

Alan Johnstone Over a year ago

Thanks for the explanation

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