Python Append List every Nth index
Given 2 list, append list to the original list every nth index.
Input : test_list = [3, 7, 8, 2, 1, 5, 8], app_list = [G, F, G], N = 3
Output : [G, F, G, 3, 7, 8, G, F, G, 2, 1, 5, G, F, G, 8]
Explanation : List is added after every 3rd element.
Input : test_list = [3, 7, 8, 2, 1, 5, 8, 9], app_list = [G, F, G], N = 4
Output : [G, F, G, 3, 7, 8, 2, G, F, G, 1, 5, 8, 9 G, F, G]
Explanation : List is added after every 4th element.
Method #1 : Using loop
This is brute way to solve this problem, in this, every nth index, inner loop is used to append all other list elements.
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# Python3 code to demonstrate working of
# Append List every Nth index
# Using loop
# initializing list
test_list = [3, 7, 8, 2, 1, 5, 8, 9, 3]
# printing original list
print["The original list is : " + str[test_list]]
# initializing Append list
app_list = ['G', 'F', 'G']
# initializing N
N = 3
res = []
for idx, ele in enumerate[test_list]:
# if index multiple of N
if idx % N == 0:
for ele_in in app_list:
res.append[ele_in]
res.append[ele]
# printing result
print["The appended list : " + str[res]]
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Output:
The original list is : [3, 7, 8, 2, 1, 5, 8, 9, 3]
The appended list : [G, F, G, 3, 7, 8, G, F, G, 2, 1, 5, G, F, G, 8, 9, 3]
Method #2 : Using extend[]
Another way to solve this problem. In this, we use extend to get all the elements in every Nth index, rather than inner list.
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# Python3 code to demonstrate working of
# Append List every Nth index
# Using extend[]
# initializing list
test_list = [3, 7, 8, 2, 1, 5, 8, 9, 3]
# printing original list
print["The original list is : " + str[test_list]]
# initializing Append list
app_list = ['G', 'F', 'G']
# initializing N
N = 3
res = []
for idx, ele in enumerate[test_list]:
# if index multiple of N
if idx % N == 0:
# extend to append all elements
res.extend[app_list]
res.append[ele]
# printing result
print["The appended list : " + str[res]]
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Output:
The original list is : [3, 7, 8, 2, 1, 5, 8, 9, 3]
The appended list : [G, F, G, 3, 7, 8, G, F, G, 2, 1, 5, G, F, G, 8, 9, 3]
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