CODEWITHSUNDEEP
pythonlist
learningstudent
learningstudent

Reputation: 577

adding 1 constant value to all sub_list in list in python

I have a list:

list1=[[2,3],[4,5],[6,7]]

I want to add a single value "one" to all sublist in the list at index 2

final output should be:

list2=[[2,3,"one"],[4,5,"one"],[6,7,"one"]]

tried with:

for list2 in list1:
    print list2.insert(2,"one")

But its showing error as None.

Upvotes: 1

Views: 946

Answers (7)

Debarpan898
Debarpan898

Reputation: 1

List_1 = [[2,3],[4,5],[6,7]]  
List_2 = [ ]
For i in List_1:             #Selecting a sub-list at each iteration
    temp = i.append('one')   #Adding 'one' to the sub-list
    List_2.append()          #Adding the modified sublist to List_2

Result:

Print(List_2)    
[[2, 3, 'one'], [4, 5, 'one'], [6, 7, 'one']]

Upvotes: 0

blhsing
blhsing

Reputation: 106891

The list.insert() function modifies the list without returning it.

You should print the list afterwards:

for list2 in list1:
    list2.insert(2,"one")
print(list1)

Alternatively, what you want to do can be more easily achieved with list comprehension:

list1=[[2,3],[4,5],[6,7]]
list2=[i + ["one"] for i in list1]
print(list2)

Both pf the above output:

[[2, 3, 'one'], [4, 5, 'one'], [6, 7, 'one']]

Upvotes: 2

Sociopath
Sociopath

Reputation: 13426

You need:

list1=[[2,3],[4,5],[6,7]]

for l in list1:
    l.append("one")

Output:

[[2, 3, 'one'], [4, 5, 'one'], [6, 7, 'one']]

Upvotes: 3

Emre Savcı
Emre Savcı

Reputation: 3070

Change your code as below :

list1=[[2,3],[4,5],[6,7]]

for subList in list1:
    subList.append("one")

print list1

Output is :

[[2, 3, 'one'], [4, 5, 'one'], [6, 7, 'one']]

Upvotes: 3

Sunitha
Sunitha

Reputation: 12015

Just use list comprehension

>>> list1 = [[2,3],[4,5],[6,7]]
>>> [e + ['one'] for e in list1]
[[2, 3, 'one'], [4, 5, 'one'], [6, 7, 'one']]

Upvotes: 2

jpp
jpp

Reputation: 164773

list.insert is an in-place operation and returns None. Instead, you can use a list comprehension:

L = [[2,3],[4,5],[6,7]]

res = [[i, j, 'one'] for i, j in L]

print(res)

[[2, 3, 'one'], [4, 5, 'one'], [6, 7, 'one']]

Upvotes: 4

running.t
running.t

Reputation: 5709

It's because list.insert in python does not return any value. So your code inserts value to list correctly but you try to print this list wrong way. It should be:

for list2 in list1:
    list2.insert(2,"one")
    print list2

Upvotes: 1

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