+ 11

Question on python lists and boolean logic and the next function

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.

2nd May 2020, 9:23 AM
M Tamim
M Tamim - avatar
4 Answers
+ 7
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.
2nd May 2020, 9:56 AM
HonFu - avatar
+ 5
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
3rd May 2020, 10:14 AM
Raja Gopal
Raja Gopal - avatar
+ 1
Ans 2. bool([()] )is a list having an element which is an empty tuple ,Whereas bool([]) is an empty list...
4th May 2020, 3:37 AM
Avinash Sharma
Avinash Sharma - avatar
heri secondary school tt hiyo kwa hiyo kama hivyo
6th May 2020, 6:20 AM
Samantha Acom
Samantha Acom - avatar