Question on python lists and boolean logic and the next function

Question

que. 1-->

a = [1,2,3]
b = a
a.append(4)
print(a) #output : [1,2,3,4]
print(b) #output : [1,2,3,4]
a = a + [5]
print(a) #output : [1,2,3,4,5]
print(b) #output : [1,2,3,4]

why did that happen?

que. 2-->

print(bool([()]) #output : True
print(bool(([])) #output : False

why the bool of ([]) is False?

que. 3-->

what is the next() func? What's it's use?

please answer if you know any single one of them.

Answer 1

Let me go backwards.

3.) next gets you the next element from a generator object/iterator.

For loops get an iterator of any collection you loop over, and automatically call next on it until nothing's left.

2.) Empty iterables are False, filled ones are true.

[()] is a list with a tuple in it, so it's true.

([]) however is just an empty list, so it's false.

You probably wanted to put a list in a tuple, but tuples with one element are written like this:

([],)

Otherwise the parentheses will just be dissolved, like when you write (1+2)*3.

Only the comma makes the tuple.

1.) b=a creates a new reference to the object.

a = a + [5] on the other hand first makes a new list of a and [5], then gives this new list the name a.

So the name a is stripped off the old object (b) and pasted onto a new one.

For details I want to link you to a tutorial about references I made that should leave close to no confusion undissolved.

https://code.sololearn.com/c89ejW97QsTN/?ref=app

If it's *not* enough, please ask.

Answer 2

1) append is used to add one element to existing list.
In the first condition the value of b=a
so in first condition a and b are having same elements

Answer 3

Ans 2. bool([()] )is a list having an element which is an empty tuple
,Whereas bool([]) is an empty list...

Answer 4

heri secondary school tt hiyo kwa hiyo kama hivyo