Python Strings Basics with Common Methods.pptx

Strings
 In programming terms, text is usually called string.
 A Python string is a sequence, which consists of zero or more characters.
 String is an immutable data structure, which means they cannot be changed.
 String is one of the most important data type in Python.
 String can be a single character or a combination of different characters.
 String literals in python are surrounded by either single quotation marks, or
double quotation marks.
'hello' is the same as "hello".
Examples
>>> a = "Hello, World!"
>>> print(a)
Hello, World!

Strings
 String is an immutable data structure, which means they cannot be
changed.
 Cannot edit the value of the variable although you can reassign it.
>>> name = “Ali Danish"
>>> name
Ali Danish
>>> name = “Jibran”
Jibran

Length and Concatenation of Strings
 To find the length of the string, len() function is used
 To join or concatenate strings, use the ‘+’ operator on strings
>>> name = "Ali Danish"
>>> name
'Ali Danish'
>>> len(name)
10
>>> name = "Ali Danish"
>>> prefix = "Mr. “
>>> prefix + name
'Mr. Ali Danish‘

Subscript Operator
 The subscript operator is defined as square brackets [].
 It is used to access the elements of string, list tuple, and so on.
 Syntax with index
<string>[index]
>>> name = "The Avengers"
>>> len(name)
12
>>> name[0]
'T'
>>> name[11]
's'

Slicing
Negative Indexing
>>> name = "The Avengers"
>>> name[-1]
's'
>>> name[-12]
'T'
>>> name[::-1]
'sregnevA ehT'

Slicing and Dicing
>>> name
'The Avengers'
>>> name[0:3]
'The‘
>>> name[:6]
'The Av'
>>> name[:]
'The Avengers'
>>> name[5:9]
'veng'
>>> name[::2]
'TeAegr'

String Case Methods
Method Expression Result
upper() name.upper() 'HELLO ALI’
lower() name.lower() 'hello ali'
capitalize() name.capitalize() ‘Hello ali'
swapcase() name.swapcase() 'hELLO aLI'
title name.title() 'Hello Ali'
name = “Hello Ali”

String Strip Methods
Method Expression Result
lstrip() name.rstrip() 'Dr Maqsood##'
rstrip() name.lstrip() '*Dr Maqsood'
strip() name.strip() 'Dr Maqsood'
name = “*Dr Maqsood##”

Split Method
Syntax: str.split(“delimiter”, num)
Split based on delimiter ‘-’
>>> str1 = "27-12-2016"
>>> str1.split("-“)
['27', '12’,’2016']
Split based on default space
>>> name = "Mohit raj"
>>> name.split()
['Mohit', 'raj']

Replace Method
syntax: str.replace(old, new max)
Relace returns copy of string with old characters are replaced with new ones
>>> str1 = "27-12-2016"
>>> str1 = "time is great and time is money"
>>> str1.replace("is","was")
'time was great and time was money‘

Join Method
syntax: str.join(seq)
seq contains sequence of separated strings here st1 acts as a separator.
>>> name = ["Mohit","raj"]
>>> " ".join(name)
'Mohit raj'

String Boolean Methods
endswith method
syntax: str.endswith(sub-string, begin,end]
>>> str1 = "Life should be great rather than long“
>>> str1.endswith("ng")
True
>>> str1.endswith("er")
False
>>> str1.endswith("er",0,27)
True

String Boolean Methods
startswith method
syntax: str.startswith(sub-string, begin,start]
>>> str1 = "Life should be great rather than long“
>>> str1.startswith("Li")
True
>>> str1.startswith("be", 11)
False
>>> str1.startswith("be", 12, 16)
True



More Boolean Methods
isalnum()
isdigit()
isspace()
islower()
isupper

Python Strings Basics with Common Methods.pptx

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