String Operators
Python provides the following operators for
string operations. These operators are useful to manipulate string.
Joining of two or more strings is called as
Concatenation. The plus (+) operator is used to concatenate strings in python.
Example
>>>"welcome" +
"Python"
'welcomePython'
Adding more strings at the end of an existing
string is known as append. The operator += is used to append a new string with
an existing string.
Example
>>> str1="Welcome
to "
str1+="Learn Python"
print (str1)
Welcome to Learn Python
(iii) Repeating (*)
The multiplication operator (*) is used to
display a string in multiple number of times.
Example
>>>str1="Welcome
"
>>>print (str1*4)
Welcome Welcome Welcome Welcome
Slice is a substring of a main string. A
substring can be taken from the original string by using [ ] operator and index
or subscript values. Thus, [ ] is also known as slicing operator. Using slice
operator, you have to slice one or more substrings from a main string.
General format of slice operation:
str[start:end]
Where start is the beginning index and end
is the last index value of a character in the string. Python takes the end
value less than one from the actual index specified. For example, if you want
to slice first 4 characters from a string, you have to specify it as 0 to 5.
Because, python consider only the end value as n-1.
Example I : slice a single character from a string
>>>str1="THIRUKKURAL"
>>>print (str1[0])
T
Example II : slice a substring from index 0 to 4
>>>print (str1[0:5])
THIRU
Example III : slice a substring using index 0 to 4
but without specifying the beginning index.
>>>print (str1[:5])
THIRU
Example IV : slice a substring using index 0 to 4 but
without specifying the end index.
>>>print (str1[6:])
KURAL
Example V : Program to slice substrings using for
loop
str1="COMPUTER"
index=0
for i in str1:
print (str1[:index+1])
index+=1
When the slicing operation, you can specify a
third argument as the stride, which refers to the number of characters to move
forward after the first character is retrieved from the string. The default
value of stride is 1.
Example
>>>str1 = "Welcome
to learn Python"
>>>print (str1[10:16])
learn
>>>print (str1[10:16:4])
r
>>>print (str1[10:16:2])
er
>>> print (str1[::3])
Wceoenyo
Note: Remember that, python takes the last value as n-1
You can also use negative value as stride
(third argument). If you specify a negative value, it prints in reverse order.
Example
>>>str1 = "Welcome
to learn Python"
>>>print(str1[::-2])
nhy re teilW
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