List operations and Slices in Python
The + operator is used to concatenate the two lists.
The + operator takes two operands. If both the operands are numeric values then the + acts as the usual addition operator. If one or both the operands are strings, then the + operator acts as string concatenation. If bot the operands are lists, then the + operator acts list concatenation.
a = [1, 2, 3] b = [4, 5, 6] c = a + b print(c)
Output
[1, 2, 3, 4, 5, 6]
#List Operation "+" l1 = [10, 20, 30] l2 = [40, 50, 60] l3 = l1 + l2 l4 = ['VTU', 'BGM'] + l1 l5 = l1 + ['VTU', 'BGM'] l6 = [10, 20, 30] + ['VTU', 'BGM'] print (l3) print (l4) print (l5) print (l6)
Output
[10, 20, 30, 40, 50, 60] ['VTU', 'BGM', 10, 20, 30] [10, 20, 30, 'VTU', 'BGM'] [10, 20, 30, 'VTU', 'BGM']
Similarly, the * operator repeats a list a given number of times:
[0] * 4
Output
[0, 0, 0, 0]
# Another Example [1, 2, 3] * 3
Output
[1, 2, 3, 1, 2, 3, 1, 2, 3]
A simple program to demonstrate the list operation *
The * takes two operands. If both the operands are numeric values then the * operator acts as the usual multiplication operator. If the first operator is a list and the second is an integer number then, the list element is repeated by the number of times the second operator.
l1 = [10, 20, 30]
print ("Before * Operation", l1)
l1 = l1 * 2
print ("After * Operation", l1)
Output
Before * Operation [10, 20, 30] After * Operation [10, 20, 30, 10, 20, 30]
List slices
The slice operator is used to extract the elements of the list.
The : is the slice operator. The following fragment of code demonstrates the slice operator on the list in python.
Program to demonstrate the List scilce on list in python
#List Slicing t = ['a', 'b', 'c', 'd', 'e', 'f'] print(t[:4]) print(t[2:]) print(t[2:5])
Output
['a', 'b', 'c', 'd'] ['c', 'd', 'e', 'f'] ['c', 'd', 'e']
Program to demnstrate the modification of list elements using scilce operator in python
t = ['a', 'b', 'c', 'd', 'e', 'f']
print ("Before modification", t)
t[1:5] = ['w','x', 'y', 'z']
print ("After modification", t)
Output
Before modification ['a', 'b', 'c', 'd', 'e', 'f'] After modification ['a', 'w', 'x', 'y', 'z', 'f']
Summary:
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