A very pythonic way of doing this would be to use list comprehension:
int_list = [[0], [1], [2], [3], [4], [5], [6]]
new_list = [value for sub_list in int_list for value in sub_list]
print(new_list)
An explaination of this can be found here: https://spapas.github.io/2016/04/27/python-nested-list-comprehensions/
There are many more ways that some people would prefer, for example a programmer who uses functional programming may prefer:
from operator import add
from functools import reduce
int_list = [[0], [1], [2], [3], [4], [5], [6]]
print(reduce(add, int_list))
If you want a more verbose and easier to understand version, you could use:
int_list = [[0], [1], [2], [3], [4], [5], [6]]
new_list = []
for i in int_list:
new_list.extend(i)
print(new_list)