how to copy list python

1new_list = old_list.copy()
2# or
3new_list = old_list[:]

1# Performance analysis by River on Stack Overflow
2METHOD                  TIME TAKEN
3b = [*a]                2.75180600000021
4b = a * 1               3.50215399999990
5b = a[:]                3.78278899999986  # Python2 winner
6b = a.copy()            4.20556500000020
7b = []; b.extend(a)     4.68069800000012
8b = a[0:len(a)]         6.84498999999959
9*b, = a                 7.54031799999984
10b = list(a)             7.75815899999997
11b = [i for i in a]      18.4886440000000
12b = copy.copy(a)        18.8254879999999  # With `import copy`
13b = []
14for item in a:
15    b.append(item)      35.4729199999997
16  
17# NOTE: Only for shallow copies, use copy.deepcopy for nested lists

1new_list = old_list.copy()
2# Above new_list does not get affected when modifying old_list
3new_list = old_list
4#Here new_list is also affected if any modifications are made to old_list

1a=[1,2,3,4]
2b=a[:] 
3''' now b has all elements of  a'''