Python array spread

As Alexander points out in the comments, list addition is concatenation.

a = [1,2,3,4]
b = [10] + a  # N.B. that this is NOT `10 + a`
# [10, 1, 2, 3, 4]
You can also use list.extend

a = [1,2,3,4]
b = [10]
b.extend(a)
# b is [10, 1, 2, 3, 4]
and newer versions of Python allow you to (ab)use the splat (*) operator.

b = [10, *a]
# [10, 1, 2, 3, 4]
Your choice may reflect a need to mutate (or not mutate) an existing list, though.

a = [1,2,3,4]
b = [10]
DONTCHANGE = b

b = b + a  # (or b += a)
# DONTCHANGE stays [10]
# b is assigned to the new list [10, 1, 2, 3, 4]

b = [*b, *a]
# same as above

b.extend(a)
# DONTCHANGE is now [10, 1, 2, 3, 4]! Uh oh!
# b is too, of course...

Source: stackoverflow.com

Similar codes

0 vote201 views1 answer
Python turtle triangle
Python
2 votes201 views1 answer
What does float mean in python
Python
0 vote213 views1 answer
How do variables work in python
Python
1 vote217 views1 answer
Exit all threads from within a thread python
Python
0 vote199 views1 answer
Print 1to 10 number without using loop in python
Python
35 votes214 views5 answers
Drop column with nan values
Python
7 votes191 views1 answer
// meaning in python
Python
1 vote188 views1 answer
Save image requests python
Python
0 vote194 views2 answers
Plt.hist bins
Python
19 votes220 views5 answers
Python autoclicker
Python