Thursday 2 November 2017

'Learn Python Visually' book

I am doing some Python study, and found the book Learn Python Visually by Ivelin Demirov in my work library.

It has the subtitle 'An Accelerated Learning Method Which Uses Science and Creativity to Teach Right-Brained Non-Coders', which is intriguing. Also, the development of the book was funded by Kickstarter, which is cool to hear!

I'm thinking to make here some notes on the new things that I learnt from this book:

p. 14. Numbers are immutable. This page explains about numbers being immutable in Python. I always find this concept really confusing. The book gave me a little more information on it, but then I also found a nice article on it on the web.
   There it is explained that when an object is initiated, it is assigned a unique object id. The state of the object can be changed later if the object is a mutable-type object. That is, the state of a mutable object can be changed after it is created, but the state of an immutable object can't be.
   The book also tells about the id() function that tells you about the identity of an object as an integer, and the is() function that compares the identity of two objects.
>>> b = 11
>>> a = b
>>> c = 12 
>>> d = 11
>>> id(a)
>>> id(b)
>>> id(c)
>>> id(d)
>>> a is b
>>> a is c
>>> a is d

p. 15 Assigning the same value to multiple variables at once. I didn't know you can assign a value to multiple variables at once:
>>> a = b = c = d = "Hello"

p. 15 Special words that can't be used as variable names. The book gives a list of special words that can't be used as variable names, I also found them on the web here.

p. 19 Using multi-line strings to store large text blocks, by enclosing them with triple quotes:
An example is:
>>> huidobro = """Al horitaña de la montazonte
La violondrina y el goloncelo
Descolgada esta mañana de la lunala
Se acerca a todo galope


p. 21 Short forms of arithmetic operators.
I knew that it was possible to do:
>>> a += 1
but it turns out that you can also do:
>>> a -= 1
>>> a *= 1
>>> a /= 2 

p. 28 Precedence of arithmetic operators. 
Something I didn't know was that exponents have precedence before subtraction, which means that we get different answers for:
>>> abs(-2 ** 2 - 20)
which first finds 2**2 = 4, and then finds abs(-4 - 20), and
>>> abs((-2) ** 2 - 20)
which first finds (-2)**2 = 4, and then finds abs(4 - 20).

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