- What is File Handling
- Why do we need this?
- Types of File Handling
- Python Read Files,
- Python Write/Create Files,
- Python Delete Files,
- What Is Json?,
- Json Load & Json Loads,
- Json Dump & Json Dumps,
- What Is Regex - Regular Expression?
- Use Of Regex- Regular Expression.
- Python Try,
- Python Except,
- Python Else,
- Python Finally,
Python provides us with an important feature for reading data from a file and writing data into a file. File handling in Python is simplified with built-in methods, which include creating, opening, and closing files. While files are open, Python allows performing various file operations, such as reading, writing, and appending information.
Files are used to store data in a storage device permanently. File handling provides a mechanism to store the output of a program in a file and to perform various operations on it. A stream is an abstraction that represents a device on which operations of input and output are performed.
Modes Description
r Open a file for reading.
w Opens a file for writing only. Overwrites the file if the file exists.
If the file does not exist, creates a new file for writing.
r+ opens for reading and writing (cannot truncate a file).
w+ For writing and reading (can truncate a file).
a Open for appending at the end of the file without truncating it.
Creates a new file if it does not exist.
t Open in text mode.
b Open in binary mode.
x Open for exclusive creation, failing if the file already.
fileobj = open('test.txt') # Open file fileobj = open('test.txt') # Open file fileobj = open('test.txt','r') # Open file in read modefileobj = open('test.txt', 'w') # Open file in write modefileobj = open('test1.txt', 'a') # Open file in append modefileobj = open('test.txt', "r") # "r" for read mode
x = fileobj.read()
print(x)What is Lorem Ipsum?
Lorem Ipsum is simply dummy text of the printing and typesetting industry. Lorem Ipsum has been the industry's standard dummy text ever since the 1500s, when an unknown printer took a galley of type and scrambled it to make a type specimen book. It has survived not only five centuries, but also the leap into electronic typesetting, remaining essentially unchanged. It was popularised in the 1960s with the release of Letraset sheets containing Lorem Ipsum passages, and more recently with desktop publishing software like Aldus PageMaker including versions of Lorem Ipsum.
Why do we use it?
It is a long established fact that a reader will be distracted by the readable content of a page when looking at its layout. The point of using Lorem Ipsum is that it has a more-or-less normal distribution of letters, as opposed to using 'Content here, content here', making it look like readable English. Many desktop publishing packages and web page editors now use Lorem Ipsum as their default model text, and a search for 'lorem ipsum' will uncover many web sites still in their infancy. Various versions have evolved over the years, sometimes by accident, sometimes on purpose (injected humour and the like).
fileobj = open('test.txt', "r")
x = fileobj.read(10) # for number of character "fileobj.read(size=-1, /)""
print(x)What is L
fileobj = open('test.txt', "r")
x = fileobj.read(100) # for number of character "fileobj.read(size=-1, /)""
print(x)What is Lorem Ipsum?
Lorem Ipsum is simply dummy text of the printing and typesetting industry. Lor
fileobj = open('test.txt', "r")
x = fileobj.readline()
print(x)What is Lorem Ipsum?
fileobj = open('test1.txt', "r")
x = fileobj.readline()
print(x)What is Lorem Ipsum?
fileobj = open('test.txt', "r")
fileobj.readlines()['What is Lorem Ipsum?\n',
"Lorem Ipsum is simply dummy text of the printing and typesetting industry. Lorem Ipsum has been the industry's standard dummy text ever since the 1500s, when an unknown printer took a galley of type and scrambled it to make a type specimen book. It has survived not only five centuries, but also the leap into electronic typesetting, remaining essentially unchanged. It was popularised in the 1960s with the release of Letraset sheets containing Lorem Ipsum passages, and more recently with desktop publishing software like Aldus PageMaker including versions of Lorem Ipsum.\n",
'\n',
'Why do we use it?\n',
"It is a long established fact that a reader will be distracted by the readable content of a page when looking at its layout. The point of using Lorem Ipsum is that it has a more-or-less normal distribution of letters, as opposed to using 'Content here, content here', making it look like readable English. Many desktop publishing packages and web page editors now use Lorem Ipsum as their default model text, and a search for 'lorem ipsum' will uncover many web sites still in their infancy. Various versions have evolved over the years, sometimes by accident, sometimes on purpose (injected humour and the like).\n",
'\n']
fileobj = open('test.txt', "r")
x = fileobj.readlines()
print(x)['What is Lorem Ipsum?\n', "Lorem Ipsum is simply dummy text of the printing and typesetting industry. Lorem Ipsum has been the industry's standard dummy text ever since the 1500s, when an unknown printer took a galley of type and scrambled it to make a type specimen book. It has survived not only five centuries, but also the leap into electronic typesetting, remaining essentially unchanged. It was popularised in the 1960s with the release of Letraset sheets containing Lorem Ipsum passages, and more recently with desktop publishing software like Aldus PageMaker including versions of Lorem Ipsum.\n", '\n', 'Why do we use it?\n', "It is a long established fact that a reader will be distracted by the readable content of a page when looking at its layout. The point of using Lorem Ipsum is that it has a more-or-less normal distribution of letters, as opposed to using 'Content here, content here', making it look like readable English. Many desktop publishing packages and web page editors now use Lorem Ipsum as their default model text, and a search for 'lorem ipsum' will uncover many web sites still in their infancy. Various versions have evolved over the years, sometimes by accident, sometimes on purpose (injected humour and the like).\n", '\n']
fileobj = open('test1.txt', "r")
x = fileobj.readlines()
print(x)['What is Lorem Ipsum?\n', "Lorem Ipsum is simply dummy text of the printing and typesetting industry. Lorem Ipsum has been the industry's standard dummy text ever since the 1500s, when an unknown printer took a galley of type and scrambled it to make a type specimen book. It has survived not only five centuries, but also the leap into electronic typesetting, remaining essentially unchanged. It was popularised in the 1960s with the release of Letraset sheets containing Lorem Ipsum passages, and more recently with desktop publishing software like Aldus PageMaker including versions of Lorem Ipsum.\n", '\n', 'Why do we use it?\n', "It is a long established fact that a reader will be distracted by the readable content of a page when looking at its layout. The point of using Lorem Ipsum is that it has a more-or-less normal distribution of letters, as opposed to using 'Content here, content here', making it look like readable English. Many desktop publishing packages and web page editors now use Lorem Ipsum as their default model text, and a search for 'lorem ipsum' will uncover many web sites still in their infancy. Various versions have evolved over the years, sometimes by accident, sometimes on purpose (injected humour and the like).\n", '\n']
file = open("test.txt","r")
for i in file:
print(i)What is Lorem Ipsum?
Lorem Ipsum is simply dummy text of the printing and typesetting industry. Lorem Ipsum has been the industry's standard dummy text ever since the 1500s, when an unknown printer took a galley of type and scrambled it to make a type specimen book. It has survived not only five centuries, but also the leap into electronic typesetting, remaining essentially unchanged. It was popularised in the 1960s with the release of Letraset sheets containing Lorem Ipsum passages, and more recently with desktop publishing software like Aldus PageMaker including versions of Lorem Ipsum.
Why do we use it?
It is a long established fact that a reader will be distracted by the readable content of a page when looking at its layout. The point of using Lorem Ipsum is that it has a more-or-less normal distribution of letters, as opposed to using 'Content here, content here', making it look like readable English. Many desktop publishing packages and web page editors now use Lorem Ipsum as their default model text, and a search for 'lorem ipsum' will uncover many web sites still in their infancy. Various versions have evolved over the years, sometimes by accident, sometimes on purpose (injected humour and the like).
fileobj = open('test.txt', "r")
x = fileobj.readlines()
print(x)
fileobj.close()['What is Lorem Ipsum?\n', "Lorem Ipsum is simply dummy text of the printing and typesetting industry. Lorem Ipsum has been the industry's standard dummy text ever since the 1500s, when an unknown printer took a galley of type and scrambled it to make a type specimen book. It has survived not only five centuries, but also the leap into electronic typesetting, remaining essentially unchanged. It was popularised in the 1960s with the release of Letraset sheets containing Lorem Ipsum passages, and more recently with desktop publishing software like Aldus PageMaker including versions of Lorem Ipsum.\n", '\n', 'Why do we use it?\n', "It is a long established fact that a reader will be distracted by the readable content of a page when looking at its layout. The point of using Lorem Ipsum is that it has a more-or-less normal distribution of letters, as opposed to using 'Content here, content here', making it look like readable English. Many desktop publishing packages and web page editors now use Lorem Ipsum as their default model text, and a search for 'lorem ipsum' will uncover many web sites still in their infancy. Various versions have evolved over the years, sometimes by accident, sometimes on purpose (injected humour and the like).\n", '\n']
fileobj = open('test.txt', "r")
fileobj.close()
fileobj.readlines()---------------------------------------------------------------------------
ValueError Traceback (most recent call last)
<ipython-input-74-633d6f0522e9> in <module>
1 fileobj = open('test.txt', "r")
2 fileobj.close()
----> 3 fileobj.readlines()
ValueError: I/O operation on closed file.
fileobj = open("test2.txt", "w") # "w" for write mode
fileobj.write("NEW CONTENT ADDED IN THE FILE.")
fileobj.close()fileobj = open('test2.txt','r') # lets check is this write?
fileobj.read()'NEW CONTENT ADDED IN THE FILE.'
fileobj = open("test2.txt", "w") # Create a new file
fileobj.write("First Line\n")
fileobj.write("Second Line\n")
fileobj.write("Third Line\n")
fileobj.write("Fourth Line\n")
fileobj.write("Fifth Line\n")
fileobj.close()fileobj = open('test2.txt','r') # lets check is this write?
print(fileobj.read())First Line
Second Line
Third Line
Fourth Line
Fifth Line
fileobj = open("test2.txt", "a") # append into previous file
fileobj.write("\n six Line\n")
fileobj.write("Seven Line\n")
fileobj.write("eight Line\n")
fileobj.write("nine Line\n")
fileobj.write("ten Line\n")
fileobj.close()fileobj = open('test2.txt','r') # lets check is this write?
print(fileobj.read())First Line
Second Line
Third Line
Fourth Line
Fifth Line
six Line
Seven Line
eight Line
nine Line
ten Line
# Python code to illustrate with()
with open("test1.txt") as file:
data = file.read()
# do something with data
print(data)
# dataWhat is Lorem Ipsum?
Lorem Ipsum is simply dummy text of the printing and typesetting industry. Lorem Ipsum has been the industry's standard dummy text ever since the 1500s, when an unknown printer took a galley of type and scrambled it to make a type specimen book. It has survived not only five centuries, but also the leap into electronic typesetting, remaining essentially unchanged. It was popularised in the 1960s with the release of Letraset sheets containing Lorem Ipsum passages, and more recently with desktop publishing software like Aldus PageMaker including versions of Lorem Ipsum.
Why do we use it?
It is a long established fact that a reader will be distracted by the readable content of a page when looking at its layout. The point of using Lorem Ipsum is that it has a more-or-less normal distribution of letters, as opposed to using 'Content here, content here', making it look like readable English. Many desktop publishing packages and web page editors now use Lorem Ipsum as their default model text, and a search for 'lorem ipsum' will uncover many web sites still in their infancy. Various versions have evolved over the years, sometimes by accident, sometimes on purpose (injected humour and the like).
# Python code to illustrate split() function
with open("test1.txt", "r") as file:
data = file.readlines()
for line in data:
word = line.split()
print (word)['What', 'is', 'Lorem', 'Ipsum?']
['Lorem', 'Ipsum', 'is', 'simply', 'dummy', 'text', 'of', 'the', 'printing', 'and', 'typesetting', 'industry.', 'Lorem', 'Ipsum', 'has', 'been', 'the', "industry's", 'standard', 'dummy', 'text', 'ever', 'since', 'the', '1500s,', 'when', 'an', 'unknown', 'printer', 'took', 'a', 'galley', 'of', 'type', 'and', 'scrambled', 'it', 'to', 'make', 'a', 'type', 'specimen', 'book.', 'It', 'has', 'survived', 'not', 'only', 'five', 'centuries,', 'but', 'also', 'the', 'leap', 'into', 'electronic', 'typesetting,', 'remaining', 'essentially', 'unchanged.', 'It', 'was', 'popularised', 'in', 'the', '1960s', 'with', 'the', 'release', 'of', 'Letraset', 'sheets', 'containing', 'Lorem', 'Ipsum', 'passages,', 'and', 'more', 'recently', 'with', 'desktop', 'publishing', 'software', 'like', 'Aldus', 'PageMaker', 'including', 'versions', 'of', 'Lorem', 'Ipsum.']
[]
['Why', 'do', 'we', 'use', 'it?']
['It', 'is', 'a', 'long', 'established', 'fact', 'that', 'a', 'reader', 'will', 'be', 'distracted', 'by', 'the', 'readable', 'content', 'of', 'a', 'page', 'when', 'looking', 'at', 'its', 'layout.', 'The', 'point', 'of', 'using', 'Lorem', 'Ipsum', 'is', 'that', 'it', 'has', 'a', 'more-or-less', 'normal', 'distribution', 'of', 'letters,', 'as', 'opposed', 'to', 'using', "'Content", 'here,', 'content', "here',", 'making', 'it', 'look', 'like', 'readable', 'English.', 'Many', 'desktop', 'publishing', 'packages', 'and', 'web', 'page', 'editors', 'now', 'use', 'Lorem', 'Ipsum', 'as', 'their', 'default', 'model', 'text,', 'and', 'a', 'search', 'for', "'lorem", "ipsum'", 'will', 'uncover', 'many', 'web', 'sites', 'still', 'in', 'their', 'infancy.', 'Various', 'versions', 'have', 'evolved', 'over', 'the', 'years,', 'sometimes', 'by', 'accident,', 'sometimes', 'on', 'purpose', '(injected', 'humour', 'and', 'the', 'like).']
[]
with open("test2.txt",'r') as x:
y = x.readlines()
print(y)['First Line\n', 'Second Line\n', 'Third Line\n', 'Fourth Line\n', 'Fifth Line\n', '\n', ' six Line\n', 'Seven Line\n', 'eight Line\n', 'nine Line\n', 'ten Line\n']
with open("test2.txt",'r') as x:
y = x.readlines()
# print(y)
y['First Line\n',
'Second Line\n',
'Third Line\n',
'Fourth Line\n',
'Fifth Line\n',
'\n',
' six Line\n',
'Seven Line\n',
'eight Line\n',
'nine Line\n',
'ten Line\n']
with open("test2.txt",'w') as x:
x.write("First Line\n")
x.write("Second Line\n")
x.write("Third Line\n")
x.write("Fourth Line\n")
x.write("Fifth Line\n")with open("test3.txt","w") as file:
file.write("Why do we use it?\n")
file.write("""It is a long established fact that a reader will be distracted by the readable content of a page
when looking at its layout. The point of using Lorem Ipsum is that it has a more-or-less normal distribution of
letters, as opposed to using 'Content here, content here', making it look like readable English. Many desktop
publishing packages and web page editors now use Lorem Ipsum as their default model text, and a search for
'lorem ipsum' will uncover many web sites still in their infancy. Various versions have evolved over the years,
sometimes by accident, sometimes on purpose (injected humour and the like).""")with open("test3.txt","r") as rd:
readd = rd.read()
print(readd)Why do we use it?
It is a long established fact that a reader will be distracted by the readable content of a page
when looking at its layout. The point of using Lorem Ipsum is that it has a more-or-less normal distribution of
letters, as opposed to using 'Content here, content here', making it look like readable English. Many desktop
publishing packages and web page editors now use Lorem Ipsum as their default model text, and a search for
'lorem ipsum' will uncover many web sites still in their infancy. Various versions have evolved over the years,
sometimes by accident, sometimes on purpose (injected humour and the like).
with open('test2.txt','a') as file:
file.write("\n six Line\n")
file.write("Seven Line\n")
file.write("eight Line\n")
file.write("nine Line\n")
file.write("ten Line\n")with open("test.txt","r") as rd:
readd = rd.read()
print(readd)What is Lorem Ipsum?
Lorem Ipsum is simply dummy text of the printing and typesetting industry. Lorem Ipsum has been the industry's standard dummy text ever since the 1500s, when an unknown printer took a galley of type and scrambled it to make a type specimen book. It has survived not only five centuries, but also the leap into electronic typesetting, remaining essentially unchanged. It was popularised in the 1960s with the release of Letraset sheets containing Lorem Ipsum passages, and more recently with desktop publishing software like Aldus PageMaker including versions of Lorem Ipsum.
Why do we use it?
It is a long established fact that a reader will be distracted by the readable content of a page when looking at its layout. The point of using Lorem Ipsum is that it has a more-or-less normal distribution of letters, as opposed to using 'Content here, content here', making it look like readable English. Many desktop publishing packages and web page editors now use Lorem Ipsum as their default model text, and a search for 'lorem ipsum' will uncover many web sites still in their infancy. Various versions have evolved over the years, sometimes by accident, sometimes on purpose (injected humour and the like).
with open('test1.txt','a') as file:
file.write("\n six Line\n")
file.write("Seven Line\n")
file.write("eight Line\n")
file.write("nine Line\n")
file.write("ten Line\n")with open("test1.txt","r") as rd:
readd = rd.read()
print(readd)What is Lorem Ipsum?
Lorem Ipsum is simply dummy text of the printing and typesetting industry. Lorem Ipsum has been the industry's standard dummy text ever since the 1500s, when an unknown printer took a galley of type and scrambled it to make a type specimen book. It has survived not only five centuries, but also the leap into electronic typesetting, remaining essentially unchanged. It was popularised in the 1960s with the release of Letraset sheets containing Lorem Ipsum passages, and more recently with desktop publishing software like Aldus PageMaker including versions of Lorem Ipsum.
Why do we use it?
It is a long established fact that a reader will be distracted by the readable content of a page when looking at its layout. The point of using Lorem Ipsum is that it has a more-or-less normal distribution of letters, as opposed to using 'Content here, content here', making it look like readable English. Many desktop publishing packages and web page editors now use Lorem Ipsum as their default model text, and a search for 'lorem ipsum' will uncover many web sites still in their infancy. Various versions have evolved over the years, sometimes by accident, sometimes on purpose (injected humour and the like).
six Line
Seven Line
eight Line
nine Line
ten Line
In r+ mode, we can read and write the file, but the file pointer position is at the beginning of the file; if we write the file directly, it will overwrite the beginning content.
See the below example:
with open('file.txt', 'r+') as f:
f.write("new line \n hello")
x = f.readlines()
print(x)[]
with open('file.txt', 'r+') as f:
f.read() # move file position to the end of the file.
f.write("new line \n")
import os
os.remove("test.txt")import os
os.remove("test1.txt")import os
os.remove("test3.txt")import os
os.remove("file.txt")JSON (JavaScript Object Notation) is a popular data format used for representing structured data. It's common to transmit and receive data between a server and web application in this format. In Python, JSON exists as a string; in other languages it's written as a series of characters.
A nonrelational database is designed to store and query data as JSON documents, rather than normalizing data across multiple tables, as in a relational database. It is often used for serializing structured data and exchanging it over a network, typically between a server and web applications. The language is relatively easy to read and write, while also easy for software to parse and generate.
Python Object JSON Object
Dict Object
List, Tuple Array
String String
Int, Float Numbers
Boolean True/False
None Null
import json
# some JSON:
x = '{ "name":"John", "age":30, "city":"New York"}'
# parse x:
y = json.loads(x)
# the result is a Python dictionary:
print(y)
print(type(y))
print(type(x)){'name': 'John', 'age': 30, 'city': 'New York'}
<class 'dict'>
<class 'str'>
import json
# JSON string:
# Multi-line string
x = """{
"Name": "Jennifer Smith",
"Contact Number": 7867567898,
"Email": "jen123@gmail.com",
"Hobbies":["Reading", "Sketching", "Horse Riding"]
}"""
# parse x:
y = json.loads(x)
# the result is a Python dictionary:
print(y){'Name': 'Jennifer Smith', 'Contact Number': 7867567898, 'Email': 'jen123@gmail.com', 'Hobbies': ['Reading', 'Sketching', 'Horse Riding']}
import json
# JSON string
employee ='{"id":"4201", "name": "Nitin", "department":"Finance"}'
# Convert string to Python dict
employee_dict = json.loads(employee)
print(employee_dict)
print(employee_dict['name']){'id': '4201', 'name': 'Nitin', 'department': 'Finance'}
Nitin
import json
# a Python object (dict):
x = {
"name": "John",
"age": 30,
"city": "New York"
}
# convert into JSON:
# conversion to JSON done by dumps() function
y = json.dumps(x)
# the result is a JSON string:
print("Result of x: ",x)
print("Result of y: ",y)
print("X ",type(x))
print("Y ",type(y))Result of x: {'name': 'John', 'age': 30, 'city': 'New York'}
Result of y: {"name": "John", "age": 30, "city": "New York"}
X <class 'dict'>
Y <class 'str'>
import json
print(json.dumps({"name": "John", "age": 30}))
print(json.dumps(["apple", "bananas"]))
print(json.dumps(("apple", "bananas")))
print(json.dumps("hello"))
print(json.dumps(42))
print(json.dumps(31.76))
print(json.dumps(True))
print(json.dumps(False))
print(json.dumps(None)){"name": "John", "age": 30}
["apple", "bananas"]
["apple", "bananas"]
"hello"
42
31.76
true
false
null
import json
# list conversion to Array
print(json.dumps(['Welcome', "to", "Python","World"]))
# tuple conversion to Array
print(json.dumps(("Welcome", "to", "Programming","World")))
# string conversion to String
print(json.dumps("Hi"))
# int conversion to Number
print(json.dumps(123))
# float conversion to Number
print(json.dumps(23.572))
# Boolean conversion to their respective values
print(json.dumps(True))
print(json.dumps(False))
# None value to null
print(json.dumps(None))["Welcome", "to", "Python", "World"]
["Welcome", "to", "Programming", "World"]
"Hi"
123
23.572
true
false
null
import json
# Creating a dictionary
Dictionary ={1:'Welcome', 2:'to',
3:'Python', 4:'for',
5:'Programming'}
# Converts input dictionary into
# string and stores it in json_string
json_string = json.dumps(Dictionary)
print('Equivalent json string of input dictionary:',json_string)
print(" ")
# Checking type of object
# returned by json.dumps
print(type(json_string))Equivalent json string of input dictionary: {"1": "Welcome", "2": "to", "3": "Python", "4": "for", "5": "Programming"}
<class 'str'>
import json
# python object(dictionary) to be dumped
dict1 ={
"emp1": {
"name": "Raheel",
"designation": "programmer",
"age": "34",
"salary": "54000"
},
"emp2": {
"name": "Ali",
"designation": "Trainee",
"age": "24",
"salary": "40000"
},
}
# the json file where the output must be stored
out_file = open("myfile.json", "w")
json.dump(dict1, out_file, indent = 6)
out_file.close()import json
# dictionary to be dumped
d ={'lang':'??? ????'}
with open('myfile.json', 'w', encoding ='utf8') as json_file:
json.dump(d, json_file, ensure_ascii = True)with open("myfile.json","r") as file:
x = file.readlines()
print(x)['{"lang": "??? ????"}']
import json
# dictionary to be dumped
d ={
'a':1,
'x':float('nan')
}
with open('myfile.json', 'w', encoding ='utf8') as json_file:
json.dump(d, json_file, allow_nan=True)with open("myfile.json","r") as file:
x = file.readlines()
print(x)['{"a": 1, "x": NaN}']
import json
x = {
"name": "John",
"age": 30,
"married": True,
"divorced": False,
"children": ("Ann","Billy"),
"pets": None,
"cars": [
{"model": "BMW 230", "mpg": 27.5},
{"model": "Ford Edge", "mpg": 24.1}
]
}
with open("make.json",'w') as y:
json.dump(x,y)
with open("make.json",'r') as file:
a=json.load(file)
print(a){'name': 'John', 'age': 30, 'married': True, 'divorced': False, 'children': ['Ann', 'Billy'], 'pets': None, 'cars': [{'model': 'BMW 230', 'mpg': 27.5}, {'model': 'Ford Edge', 'mpg': 24.1}]}
# Python program to read
# json file
import json
# Opening JSON file
f = open('myfile.json')
# returns JSON object as
# a dictionary
data = json.load(f)
print(data)
# Iterating through the json
# list
for x,y in data.items():
print(x,y)
# Closing file
f.close(){'a': 1, 'x': nan}
a 1
x nan
with open("myfile.json", "r") as read_it:
data = json.load(read_it)
print(data){'a': 1, 'x': nan}
Regular Expressions are used to match strings of text such as particular characters, words, or patterns of characters. RegEx can be used to check if a string contains the specified search pattern. It means that we can match and extract any string pattern from the text with the help of regular expressions.
Metacharacters are characters that are interpreted in a special way by a RegEx engine. Here's a list of metacharacters:
[] . ^ $ * + ? {} () \ |
import re
txt = "The rain in Spain"
x = re.search("^The.*Spain$", txt)
print(x)<re.Match object; span=(0, 17), match='The rain in Spain'>
import re
pattern = '^a...s$'
test_string = 'abyss'
result = re.match(pattern, test_string)
if result:
print("Search successful.")
else:
print("Search unsuccessful.")Search successful.
import re
txt = "The rain in Spain"
x = re.findall("ai", txt)
print(x)['ai', 'ai']
# A Python program to demonstrate working of
# findall()
import re
# A sample text string where regular expression
# is searched.
string = """Hello my Number is 123456789 and my friend's number is 987654321"""
# A sample regular expression to find digits.
regex = '\d+'
match = re.findall(regex, string)
print(match)
['123456789', '987654321']
import re
# \d is equivalent to [0-9].
p = re.compile('\d')
print(p.findall("I went to him at 11 A.M. on 4th July 1886"))
# \d+ will match a group on [0-9], group
# of one or greater size
p = re.compile('\d+')
print(p.findall("I went to him at 11 A.M. on 4th July 1886"))['1', '1', '4', '1', '8', '8', '6']
['11', '4', '1886']
Code is executed in a series of blocks, starting with the try- and except blocks. The finally block lets you execute code, regardless of the result of the first two blocks. Code can only be executed once if there is an exception or when there is no error.
The try-except statement is a Microsoft extension to the C language that enables applications to gain control of a program when events that normally terminate execution occur. Such events are called exceptions, and the mechanism that deals with them is called structured exception handling (TEW).
try:
# Some Code
except:
# Executed if error in the
# try block
else:
# execute if no exception
finally:
# Some code .....(always executed)
try:
a=2
print(a)
except:
print("variable is not defined!")2
try:
a=2
print(x) # x is not define
except:
print("variable is not defined!")['ai', 'ai']
if y==y:
print(y)
else:
print("Else")Else
try:
print("The value of y: ",y)
except:
print("Error")The value of y: nan
try:
print(20/2)
except:
print('Exception occured') # This statement will be execu10.0
a = [1, 2, 3]
try:
print ("Second element = %d" %(a[1]))
# Throws error since there are only 3 elements in array
print ("Fourth element = %d" %(a[4]))
except:
print ("An error occurred") Second element = 2
An error occurred
try:
a=2
print(a)
except:
print("variable is not defined!")
else: # this will have to execute
print("hey!")2
hey!
try:
a = int(input("Enter a:"))
b = int(input("Enter b:"))
c = a/b
print("a/b = %d"%c)
print(c)
# Using Exception with except statement. If we print(Exception) it will return exception class
except:
print("can't divide by zero")
# print(Exception)
else:
print("Hi I am else block") Enter a:45
Enter b:46
a/b = 0
0.9782608695652174
Hi I am else block
try:
print("Hello")
except:
print("Something went wrong")
else:
print("Nothing went wrong")Hello
Nothing went wrong
# program to print the reciprocal of even numbers
try:
num = int(input("Enter a number: "))
assert num % 2 == 0
except:
print("Not an even number!")
else:
reciprocal = 1/num
print(reciprocal)Enter a number:
Not an even number!
try:
a = int(input("Enter a:"))
b = int(input("Enter b:"))
c = a/b
print("a/b = %d"%c)
print(c)
# Using Exception with except statement. If we print(Exception) it will return exception class
except:
print("can't divide by zero")
# print(Exception)
finally:
print("Hi I am finally block") Enter a:467
Enter b:8
a/b = 58
58.375
Hi I am finally block
try:
k = 5//0 # raises divide by zero exception.
print(k)
# handles zerodivision exception
except:
print("Can't divide by zero")
finally:
# this block is always executed
# regardless of exception generation.
print('This is always executed')Can't divide by zero
This is always executed