What are the differences between numpy arrays and matrices? Which one should I use?

Numpy matrices are strictly 2-dimensional, while numpy arrays (ndarrays) are N-dimensional. Matrix objects are a subclass of ndarray, so they inherit all the attributes and methods of ndarrays. The main advantage of numpy matrices is that they provide a convenient notation for matrix multiplication: if a and b are matrices, then a*b is their matrix product. On the other hand, as … Read more

How does str(list) work?

Well you have a total of 4 questions, let us go one by one. 1. Why does str(list) returns how we see list on the console? How does str(list) work? What is str() and __str__()? The str() callable is to return a printable form of the object only! From the docs str(object) does not always attempt to return a string that is acceptable to eval(); its goal is to return a … Read more

urllib and “SSL: CERTIFICATE_VERIFY_FAILED” Error

If you just want to bypass verification, you can create a new SSLContext. By default newly created contexts use CERT_NONE. Be careful with this as stated in section 17.3.7.2.1 When calling the SSLContext constructor directly, CERT_NONE is the default. Since it does not authenticate the other peer, it can be insecure, especially in client mode where most of time you … Read more

What is key=lambda

A lambda is an anonymous function: It is often used in functions such as sorted() that take a callable as a parameter (often the key keyword parameter). You could provide an existing function instead of a lambda there too, as long as it is a callable object. Take the sorted() function as an example. It’ll return the given iterable in sorted order: but that sorts uppercased … Read more

Using unicode character u201c

The reason is that in 3.x Python You can’t just mix unicode strings with byte strings. Probably, You’ve read the manuals dealing with Python 2.x where such things are possible as long as bytestring contains convertable chars. works fine for me, so the only reason is that you’re using wrong encoding for source file or … Read more