0
list1 = input("list aval ra vared kon:   ").split()
list2 = input("list dovom ra vared kon:   ").split()

#I do not understand the following line
list1 [ : 0] = list2

print("javab is :  " , list1)
sj95126
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سید علیرضا طباطبایی
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    It's the same thing as `list1 = list2 + list1`, but written by someone who thinks they're really clever. – Silvio Mayolo Aug 01 '22 at 04:39
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    @SilvioMayolo: Technically, it's slightly different, because the first one modifies the existing `list1` and the second one replaces it with a new list. – sj95126 Aug 01 '22 at 04:44

1 Answers1

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The line of code: list1 [ : 0] = list2 adds all the value of list2 directly into list1 The values added are before the actual values of list1.

For Instance, take this example,

list1 = ['a', 'b', 'c', 'd', 'e']
list2 = [1, 2, 3, 4, 5]
# Case 1
list1 [:0] = list2 # list1 = [1, 2, 3, 4, 5, 'a', 'b', 'c', 'd', 'e']

# Case 2
list1 [:1] = list2 # list1 = [1, 2, 3, 4, 5, 'b', 'c', 'd', 'e']

#Case 3
list1 [:2] = list2 # list1 = [1, 2, 3, 4, 5, 'c', 'd', 'e']

The syntax list[start:stop] is used to slice lists into smaller parts. For more information, see this StackOverflow Post: Understanding slicing

The [:0] shows that all the elements in list2 must be inserted into list1 before the 0th element(First Item in list1)

Had you inserted [:1], the element before in list1 ('a' -> list1[0]) would have been replaced with the values present in list2

Hope this helps.

Programmer-X31
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