I'm confused as to why the following code answer is:
import numpy as np
dt=[('name','S16'),('grad',int),('cpg',float)]
val=[("Ahmadmm",2008,12),('ali',2010,12.2),('mitra',505,15.15)]
arr=np.array(val,dtype=dt)
print(arr)
output: [(b'Ahmadmm', 2008, 12. ) (b'ali', 2010, 12.2 ) (b'mitra', 505, 15.15)]
Why there is a 'b' before each string?
I think this post answers your question: What does the 'b' character do in front of a string literal?. The 'b' character is basically indicating a byte literal.
As NPE stated in this question, to quote the Python 2.x documentation:
A prefix of 'b' or 'B' is ignored in Python 2; it indicates that the literal should become a bytes literal in Python 3 (e.g. when code is automatically converted with 2to3). A 'u' or 'b' prefix may be followed by an 'r' prefix.
The Python 3 documentation states:
Bytes literals are always prefixed with 'b' or 'B'; they produce an instance of the bytes type instead of the str type. They may only contain ASCII characters; bytes with a numeric value of 128 or greater must be expressed with escapes.
('name','S16')use('name', ' U16'). S mean the string datatype, U is the Unicode one. — Then the output will be[('Ahmadmm', 2008, 12. ) ('ali', 2010, 12.2 ) ('mitra', 505, 15.15)]