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Python Strings
Balasaheb Garule
2 years ago
Table of Content
What are Python Strings?
Declare Python String?
Use Quotes inside Python String
Spanning a String Across Multiple Lines
Python String Operations
Access the Python String
1. How to display a single character?
2. How to Slicing a String in Python?
3. Reverse a String using Slicing
Python String Concatenation
Python String Formating
1. f-strings
2. format() method
3. % operator
Escape Sequences in Python
String Conversion
- Python string to int
- Python string to list
- Python str to float
Python String Functions
1. len()
2. str()
3. lower() and upper()
4. strip()
5. isdigit()
6. isalpha()
7. isspace()
8. startswith()
9. endswith()
10. find()
11. replace()
12. split()
13. join()
Summary
What are Python Strings?
Python strings are sequences of characters. It is an ordered collection and immutable.’str’ class is used for python strings. Identify the class of variables using the type() method.
e.g.
type(“Cats are cute”)Output
<class ‘str’>Python doesn’t support char data-type like C++ or Java.
Declare Python String
We can use single quotes (‘’) or double quotes for declaring python strings.
e.g.
s='Cats are cute' # python string example
print(s)Output
Cats are cutes=" Cats are cute " # python string example
print(s)Output
Cats are cuteHowever, you cannot use both quotation marks for declaring string.
e.g.
s= ‘Cats are cute” # python string exampleOutput
SyntaxError: EOL while scanning string literalUse Quotes inside Python String
We cannot use the same quotation mark for use of quotes inside the python string.
s="Cats are "cute"" # python string exampleOutput
SyntaxError: invalid syntaxFor a double quote, we can use single quotes or for a single quote, we can use double-quotes.
s=’Cats are "cute"' # python string example
print(s)Output
Cats are “cute”Or
s="Cats are 'cute'" # python string example
print(s)Output
Cats are ‘cute’You can use multiple quotes.
e.g.
s="'Cats' 'are' 'cute'" # python string example
print(s)Output
‘Cats’ ‘are’ ‘cute’Spanning a String Across Multiple Lines
For spanning a string across multiple lines we can use triple quotes.
s="""Welcome
to
insideaiml""" # python string example
print(s)Output
Welcome
to
insideaimlWe can use a backward slash to preserve the newline in the program but not in the program output.
e.g.
s="""Welcome\
to\
insideaiml""" # python string example
print(s)Output
Welcome to insideaimlPython String Operations
Following are the python string operations
Access the Python String
A string is immutable; it can’t be modified.
s="Cats"
s[0]="H"Output
Traceback (most recent call last):File “<pyshell#22>”, line 1, in <module>
s[0]=”H”
TypeError: ‘str’ object does not support item assignmentBut you can access a string. . .
s="Cats are cute" # python string example
sOutput
‘Cats are cute’
print(s)Output
Cats are cute How to display a single character?
We can use indexing to display a single character. index starts from 0.
s="Cats are cute"
s[1]Output
‘a’How to Slicing a String in Python?
Slicing a string in python using the following syntax.
str_object[start_pos:end_pos:step]
e.g.
s="Cats are cute"
s[3:8]Output
‘s are’Here, end_pos is excluded. Index start from 0.
e.g.
s[:8]Output
‘Cats are’This prints characters from the start to character 7.
s[9:]Output
‘ ut’This prints characters from character 9 to the end of the string.
s[:]Output
‘Cats are cute’This prints the whole string.
s[:-2]Output
‘Cats are cu’It starts printing the character from the beginning to the second last character from the end.
s[-2:]Output
‘te’It prints characters from the second last character from the end to the end of the string.
s[-3:-2]Output
‘u’It prints characters from three characters from the end of a string to the second last character.
It returns empty strings.
s[-3:-3]Output
” s[3:3]Output
‘’Reverse a String using Slicing
Reverse the string using slicing.
e.g.
s = 'insideaiml'
reverse_str = s[::-1]
print(reverse_str)Output
lmiaedisniList of strings in python
# list of strings in python
names = ["amol", "rohan", "manisha"]
# print the list of strings
print(names)
[‘amol’, ‘rohan’, ‘manish’]
# loop over the names list, and print each string one at a time
for name in names:
print(name)Output
amol
rohan
manishaPython String Concatenation
Python string concatenation is combining the strings. Python Strings can combine using the concatenation operator ”+”.
e.g.
x='Welcome to, '
y='insideaiml'
x+y # Python string concatenationOutput
‘Welcome to insideaiml’ e.g.
s='bye 'print(2*s)Output
bye byewe can not concatenate strings into numbers.
e.g.
'40'+10Output
Traceback (most recent call last):
File "<string>", line 1, in <module>
TypeError: can only concatenate str (not "int") to strPython String Formatting
We can format python strings simply using the commas in the print() method.
e.g.
city=Pune
print("Age:",30,"City:",city)Output
Age: 30 City: PuneIn python, formatting methods are available as follows:
f-strings
f-string python formatting technique use for formatting the string using the letter ‘f’ precedes the string, and the variables are used using curly braces “{}” in their places.
e.g.
name = ”insiadeaiml”
print(f"Welcome to {name}") # f string pythonOutput
Welcome to insideaimlformat() method
format() method use to format python string.It use argument separated by commas.
Syntax:
String.format(value1, value2,)
We can use it three ways
str1 = "My name is {fname} and roll no is {rollno}".format(fname = "Rohan",rollno= 1)
str2 = "My name is {0} and roll no is {1} ".format( "Rohan", 1)
str3 = "My name is {} and roll no is {}".format( "Rohan", 1)
print(str1)
print(str2)
print(str3) Output
My name is Rohan and roll no is 1
My name is Rohan and roll no is 1
My name is Rohan and roll no is 1I love cats% operator
% operator used for to access variable.%s is used for string
e.g.
Str1='Cats'
Str2 =’Dogs’
print("I love %s and %s" %(Str1,Str2))Output
I love Cats and Dogs%d is used for integers and %f used for floating-point numbers
Escape Sequences in Python
In Python following sequences are available.
\' Single Quote
\\ Backslash
\n New Line
\r Carriage Return
\t Tab
\b Backspace
\f Form Feed
\ooo Octal value
\xhh Hex value
e.g.
str1 = 'It\'s Amazing.'
print(str1)
str2 = "This will insert one \\ (backslash)."
print(str2)
str3 = "Hello\nWorld!"
print(str3)
str4 = "Hello\rWorld!"
print(str4)
str4 = "Hello\tWorld!"
print(str4)
#This example erases one character (backspace):
str5 = "Hello \bWorld!"
print(str5)
#A backslash followed by three integers will result in a octal value:
Str6 = "\151\156\163\151\144\145\141\151\155\154"
print(str6)
#A backslash followed by an 'x' and a hex number represents a hex value:
str7 ="\x69\x6e\x73\x69\x64\x65\x61\x69\x6d\x6c"
print(str7)Output
It's Amazing.
This will insert one \ (backslash).
Hello
World!
Hello
World!
Hello World!
Hello World!
insideaiml
insideaimlString Conversion
Python string to int
We can use the int() method to convert a python string to int.
e.g.
s = “100”
print(type(s))
n = int(s)
print(type(n))
print(n)output
<class 'str'>
<class 'int'>
100Python String to list
To convert python string to list need a split() method which use delimiter as argument
syntax:
string.split(delimiter)
e.g.
s = “welcome to insideaiml”
list1 = s.split(“ “) #use delimiter as a space “ “output
list1
['welcome', 'to', 'insideaiml'] #string to list in pythonExample demonstrates the string to list in python conversion.
Python str to float
Python str to float type conversion uses float() method.
e.g.
s = "3.14"
print(s)
print(type(s))
dec = float(s) #string to float in python
print(dec)
print(type(dec))output
3.14
<class 'str'>
3.14
<class 'float'> #string to float in pythonPython String Functions
Python provides us with several functions that we can apply on strings or to create strings.
len()
It returns the length of the string
s='insideaiml'
len(s)Output
10It also uses it to find the length of a slice of the string is.
e.g.
len(s[2:])Output
8str()
str in python used for type casting into string.str in python converts int to string, float to string, complex to string and so on.
e.g.
s= str(5+3j)
print(type(s))
print(s)Output
<class 'str'>
(5+3j)lower() and upper()
Get uppercase and lowercase strings using lower() method and upper()method respectively.
s=”Python”
a.lower()Output
pythons.upper()Output
PYTHONstrip()
Strip() method removes whitespaces from the beginning and end of the string.
s=' Python '
s.strip()Output
‘Python’isdigit()
If the string contains all digit returns True.
e.g.1
s=”555”
s.isdigit()Output
Truee.g. 2
s='pi3.14'
a.disdigit()Output
Falseisalpha()
If string character is alphabat then returns True.
s=’python’
s.isalpha()Output
Trues='abc4'
s.isalpha()Output
Falseisspace()
If string is space characters return True.
e.g.
s=' '
s.isspace()Output
Trues=' ab '
s.isspace()Output
Falsestartswith()
It used to check if a string started with a specified character or word.
e.g
s=”insideaiml”
s.startswith('in')Output
Trueendswith()
It used to check string end with specified character or word.
s=”python”
s.endswith('on')Output
Truefind()
It used to find provided substring into string.
e.g.
# check if the string contains substring python
s=”insideaiml”
s.find(side)Output
2Return -1 if substring is not found.
s.find(on)Output
-1replace()
It replaces substring in the provided string. It takes two arguments part of a string which is replaced by substring.
“Mohan”.replace(‘Mo’, 'Ro')Output
‘Rohan’split()
It split the string using provided argument.
e.g.
'I, am, Student'.split(',')Output
[‘I’, ‘ am’, ‘ student’]join()
It is used to join the strings using separator.
e.g.
"+".join(['jan','feb','march'])Output
'jan+feb+march'Summary
In this blog, we learned about python strings with string functions and Operators, and how to declare and access them.
We also learned about python string concatenation and formatters in python.
Finally, we learned about Python string functions that we can perform on strings.
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