Strings

Strings are used in Python to record text information, such as names. 

Strings in Python are actually a sequence, which basically means Python keeps track of every element in the string as a sequence. 

For example, Python understands the string "hello' to be a sequence of letters in a specific order. This means we will be able to use indexing to grab particular letters (like the first letter, or the last letter).

This idea of a sequence is an important one in Python and we will touch upon it later on in the future.

In this blog we'll learn about the following:

• Creating Strings
• Printing Strings
• String Methods
• String Indexing
• String Slicing
• String Properties

Creating String:

1] Strings can be created as below using single quotes or double quotes

strVar = 'Python'
strVar1 = "python"

2] A multi-line string can declared with triple quotes as below:
strVar2 = """python language
is easy to learn"""

3] A string declaration with quotes should be handled properly. For example, if we created any quote[either single or double quotes] line, we have to use combinations of double and single quotes to get the complete statement like below

print("hello Jane's ")

print('Hello Mr" hw are u')

o/p - 

hello Jane's 

Hello Mr" hw are u

Printing String: 

1] For above declared strings, output will be printed like below: 

print("Output of String Var:", strVar)
print("Output of String Var1:", strVar1)
print("Output of String Var2:", strVar2)
o/p -
Output of String Var: Python 

Output of String Var1: python 

Output of String Var2: python language 

is easy to learn

2] We can use the .format() method to add formatted objects to printed string statements

print("Curly bracket is to insert another string: {}".format('New string'))

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Curly bracket is to insert another string: New string

Basic Built-in String methods

1] replace() is to replace the strings from string variable
Syntax will be, String_name.replace("text what to replace", "New text")

strVarNew = strVar2.replace("language", "programming language")
print("\nString Var2 is:", strVar2)
print("Output of String Var New:", strVarNew)
o/p -
String Var2 is: python language

is easy to learn 

Output of String Var New: python programming language 

is easy to learn


2] len() to find length the string
print("\nString Var1 is :", strVar1)
print("Length of string Var 1:", len(strVar1))
o/p -
String Var1 is : python 

Length of string Var 1: 6

String indexing

Since strings are a sequence, which means Python can use indexes to call parts of the sequence. Let's learn how this works.

print("\nString var1 is", strVar1)
print("First index in str var1 is", strVar1[0])
print("Second index in str var1 is", strVar1[1])
o/p -
String var1 is python 

First index in str var1 is p 

Second index in str var1 is y

String Slicing

This will be defined in format as [start index: stop index: step size]

• Here start index, the index from where slice need to start
• Stop index is upto where slicing need to done. So this index value wont include in slicing output
• step size, by default it will be 1, so if we want to change we can include the step size
• Slicing can be used to reverse the string also. 

print("\nString Var is :", strVar)
print("Start index slicing - string var", strVar[1:])
print("Stop index slicing - string var:", strVar[:3])
print("Using step size - string Var:", strVar[::3])
print("Using slicing to reverse a string:", strVar[::-1])
o/p -
String Var is : Python 

Start index slicing - string var ython 

Stop index slicing - string var: Pyt 

Using step size - string Var: Ph 

Using slicing to reverse a string: nohtyP

String Properties

1] Strings have an important property known as immutability. This means that once a string is created, the elements within it can not be changed or replaced.

Trying to assigned string index of strVar, got "typeError"

strVar[0] = 'H'

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Traceback (most recent call last): 

 File "string.py", line 41, in <module> 

 strVar[0] = 'H' 

TypeError: 'str' object does not support item assignment

2] Since we can't replace existing string, we can add string to existing string. This can be done through concatenation. 

strVar = strVar + "maestro"
print("\nConcanate string output:", strVar)
o/p -
Concanate string output: Pythonmaestro