Python - String Concatenation

The "+" operator is well-known as an addition operator, returning the sum of two numbers. However, the "+" symbol acts as string concatenation operator in Python. It works with two string operands, and results in the concatenation of the two.

The characters of the string on the right of plus symbol are appended to the string on its left. Result of concatenation is a new string.

str1="Hello"
str2="World"
print ("String 1:",str1)
print ("String 2:",str2)
str3=str1+str2
print("String 3:",str3)

It will produce the following output −

String 1: Hello
String 2: World
String 3: HelloWorld

To insert a whitespace between the two, use a third empty string.

str1="Hello"
str2="World"
blank=" "
print ("String 1:",str1)
print ("String 2:",str2)
str3=str1+blank+str2
print("String 3:",str3)

It will produce the following output −

String 1: Hello
String 2: World
String 3: Hello World

Another symbol *, which we normally use for multiplication of two numbers, can also be used with string operands. Here, * acts as a repetition operator in Python. One of the operands must be an integer, and the second a string. The operator concatenates multiple copies of the string. For example −

>>> "Hello"*3
'HelloHelloHello'

The integer operand is the number of copies of the string operand to be concatenated.

Both the string operators, (*) the repetition operator and (+) the concatenation operator, can be used in a single expression. The "*" operator has a higher precedence over the "+" operator.

str1="Hello"
str2="World"
print ("String 1:",str1)
print ("String 2:",str2)
str3=str1+str2*3
print("String 3:",str3)
str4=(str1+str2)*3
print ("String 4:", str4)

To form str3 string, Python concatenates 3 copies of World first, and then appends the result to Hello

String 3: HelloWorldWorldWorld

In the second case, the strings str1 and str2 are inside parentheses, hence their concatenation takes place first. Its result is then replicated three times.

String 4: HelloWorldHelloWorldHelloWorld

Apart from + and *, no other arithmetic operator symbols can be used with string operands.

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