String is basically “sequence of characters”.
Characteristics of String:
- Indexing in a string:
It is used to refer to a particular character present in string, considering the counting starts from 0.
Example:
parrot=”Blue”
print(parrot[0])
//output: B
- Negative Indexing in String:
It is used to count backward or from end of string
Example:
parrot=”Blue”
print(parrot[-1])
// output: e
i.e String Length – Positive Index Number= Negative Index Number
- Slicing:
It is used to slice the string and print character from start position to end position or extract a portion of string and print it .
Example:
parrot=”Norwegian”
print(parrot[0:6])
//output:Norweg
i.e above output printed characters from 0 (start position to upto 6 but not including 6th character )
Note: If we leave start value it defaults to start position
Example:
print(parrot[ :6])
//output:Norweg
If we leave end value it defaults to last character
Example:
print(parrot[2: ])
//output:rwegian
- Step in a Slice:
Step is the stride between indices .
So the syntax is string[start:stop:step]
Example: Let’s say you have the string my_string = “Hello, Python!” and you want to extract every second character from the first five characters:
my_string = "Hello, Python!“
print(my_string[0:5:2])
//output:Hlo
- Slicing Backwards or Reverse Slicing:
With a negative step value , start value default to end of string and stop value default to start of string if not given.
Example:
letters="Blue"
print[3:0:-1]
//output:eul
print[3::-1]
//output:eulB
Common String Operations :
- String Concatenation :
This operation is used to add two string .
Example:
string1=”Hello” string2=”World”
print(string1+string2)
//output: “HelloWorld”
- Repetition/ Multiplication:
This operation is used to repeat the given string “n” number of times.
Example:
print(“Hello” * 5)
//output :”HelloHelloHelloHelloHello”
- Substring in a string:
“in” operator is used to find substring in string.
Example:
today=”Friday"
print(“day” in today)
//output: True
above output returns a True (bool value ) if day is a substring in Friday else it returns False(bool value)
- String Replacement Fields:
In Python every data type can be coerced into a string representation using “str”. Example:
age =24
print(“My age is “ + age )
//output :Error
As we are trying to concatenate two different data type string and integer . To do so we have to change type of age . So
print(“My age is “ + str(age) +” years“)
//output: My age is 24 years.
- String Formatting :
Python 3 allows string to be formatted using replacement field and dot method.
Example:
age =24
print(“My age is {0} years “.format(age))
//output: My age is 24 years
In the above output the value inside {} is replaced by the variable in format .
print(“ There are {0} days in {1} {2}”.format(31, “jan”, “mar”))
0 here is for first value in format ,
1 for second value and so on.
