Python Python-Confused in list comprehension-:

[shivajikobardan]

Python-Confused in list comprehension-:

I want to find difference between two list. I came across sth called list comprehension. I can't tell you how confused I am with this.

# Python 3 code to demonstrate
# to remove elements present in other list
# using list comprehension

# initializing list1
list1 = [1, 3, 4, 6, 7]

# initializing list2
list2 = [3, 6]

# printing list1
print("The list1 is : " + str(list1))

# printing list2
print("The list2 is : " + str(list2))

# using list comprehension to perform task
res = [i for i in list1 if i not in list2]

# printing result
print("The list after performing remove operation is : " + str(res))

My confusion lies here-:

res = [i for i in list1 if i not in list2]

What is happening here? I can't understand a single word. How to understand this please guide me.

Also can you guide a link to how to write latex in this site(how to write math? I am familiar with stackexchange mathjax can I use that here???)

 

[simong1993]

Lets pull this apart and go from there 🙂 So we have our two lists, List 1 and List 2. If we was to do

for i in list1:
    print(i)

our output would be :-
1
3
4
6
7

So what your res is doing is this :-

complete = []
for i in list1:
    if i not in list2:
        complete.append(i)

i have had to add a new list called complete to simplify this but with the other way you are simply add the variable to i. What you are doing in a nut shell is loading the first record in list1 (for i in list1🙂 so 1. we then check to see if 1 is in list 2 by doing (if i not in list2🙂 if its not in list 2 then we append this to a new list called complete (complete.append(i)) we then print this at the end