python

python regular expression match, search and findall

Python regular expression match, search and findall

Python beginners may sometimes get confused by this match and search functions in the regular expression module, since they are accepting the same parameters and return the same result in most of the simple use cases.  In this article, let’s discuss about the difference between these two functions.

match vs search in Python regular expression

Let’s start from an example. Let’s say if we want to get the words which ending with “ese” in the languages, both of the below match and search return the same result in match objects.

import re
languages = "Japanese,English"
m = re.match("\w+(?=ese)",languages)
#m returns : <re.Match object; span=(0, 5), match='Japan'>

m = re.search("\w+(?=ese)",languages)
#m returns : <re.Match object; span=(0, 5), match='Japan'>

But if the sequence of your languages changed, e.g. languages = “English, Japanese”, then you will see some different results:

languages = "English,Japanese" 
m = re.match("\w+(?=ese)",languages) 
#m returns empty
m = re.search("\w+(?=ese)",languages) 
#m returns : <re.Match object; span=(8, 13), match='Japan'>

The reason is that match function only starts the matching from the beginning of your string, while search function will start matching from anywhere in your string. Hence if the pattern you want to match may not start from the beginning, you shall always use search function.

In this case, if you want to restrict the matching only start from the beginning, you can also achieve it with search function by specifying “^” in your pattern:

languages = "English,Japanese,Chinese" 
m = re.search("^\w+(?=ese)",languages) 
#m returns empty
m = re.search("\w+(?=ese)",languages)
#m returns: <re.Match object; span=(8, 13), match='Japan'>

findall in Python regular expression

You may also notice when there are multiple occurrences of the pattern, search function only returns the first matched. This sometimes may not be desired when you actually want to see the full list of matched patterns. To return all the occurrences, you can use the findall function:

languages = "English,Japanese,Chinese,Burmese"
m = re.findall("\w+(?=ese)", languages)
#m returns: ['Japan', 'Chin', 'Burm']

 

 

python send email with attachment via smtplib

How to send email with attachment via python smtplib

In one of my previous article, I have discussed about how to send email from outlook application. That has assumed you have already installed outlook and configured your email account on the machine where you want to run your script. In this article, I will be sharing with you how to automatically send email with attachments via lower level API, to be more specific, by using python smtplib where you do not need to set up anything in your environment to make it work.

For this article, I will demonstrate to you to send a HTML format email from a gmail account with some attachment. So besides the smtplib module, we will need to use another two modules – ssl and email.

Let’s get started!

First, you will need to find out the SMTP server and port info to send email via google account. You can find this information from this link. For your easy reading, I have captured in the below screenshot.

codeforests - google smtp server configuration info

So we are going to use the server: smtp.gmail.com and port 587 for our case. (you may search online to find out more info about the SSL & TLS, we will not discuss much about it in this article)

Let’s start to import all the modules we need:

import smtplib, ssl
from email.mime.multipart import MIMEMultipart 
from email.mime.text import MIMEText 
from email.mime.application import MIMEApplication

As we are going to send the email in HTML format (which are you able to unlock a lot features such as adding in styles, drawing tables etc.), we will need to use the MIMEText. And also the MIMEMultipart and MIMEApplication for the attachment.

Build up the email message

To build up our email message, we need to create mixed type MIMEMultipart object so that we can send both text and attachment. And next, we shall specify the from, to, cc and subject attributes.

smtp_server = 'smtp.gmail.com'
smtp_port = 587 
#Replace with your own gmail account
gmail = 'yourmail@gmail.com'
password = 'your password'

message = MIMEMultipart('mixed')
message['From'] = 'Contact <{sender}>'.format(sender = gmail)
message['To'] = 'contact@company.com'
message['CC'] = 'contact@company.com'
message['Subject'] = 'Hello'

You probably do not want anybody can see your hard coded password here, you may consider to put this email account info into a separate configuration file. Check my another post on the read/write configuration files.

For the HTML message content, we will wrap it into the MIMEText, and then attach it to our MIMEMultipart message:

msg_content = '<h4>Hi There,<br> This is a testing message.</h4>\n'
body = MIMEText(msg_content, 'html')
message.attach(body)

Let’s assume you want to attach a pdf file from your c drive, you can read it in binary mode and pass it into MIMEApplication with MIME type as pdf. Take note on the additional header where you need to specify the name your attachment file.

attachmentPath = "c:\\sample.pdf"
try:
	with open(attachmentPath, "rb") as attachment:
		p = MIMEApplication(attachment.read(),_subtype="pdf")	
		p.add_header('Content-Disposition', "attachment; filename= %s" % attachmentPath.split("\\")[-1]) 
		message.attach(p)
except Exception as e:
	print(str(e))

If you have a list of the attachments, you can loop through the list and attach them one by one with the above code.

Once everything is set properly, we can convert the message object into to a string:

msg_full = message.as_string()

Send email

Here comes to the most important part, we will need to initiate the TLS context and use it to communicate with SMTP server.

context = ssl.create_default_context()

And we will initialize the connection with SMTP server and set the TLS context, then start the handshaking process.

Next it authenticate our gmail account, and in the send mail method, you can specify the sender, to and cc (as a list), as well as the message string. (cc is optional)

with smtplib.SMTP(smtp_server, smtp_port) as server:
	server.ehlo()  
	server.starttls(context=context)
	server.ehlo()
	server.login(gmail, password)
	server.sendmail(gmail, 
				to.split(";") + (cc.split(";") if cc else []),
				msg_full)
	server.quit()

print("email sent out successfully")

Once sendmail completed, you will disconnect with the server by server.quit().

With all above, you shall be able to receive the email triggered from your code. You may want to wrap these codes into a class, so that you can reuse it as service library in your multiple projects.

 

As per always, please share if you have any questions or comments.

python cache

How to print colored message on command line terminal window

When you are developing a python script with some output messages printed on the terminal window, you may find a little bit boring that all the messages are printed in black and white, especially if some messages are meant for warning, and some just for information only. You may wonder how to print colored message to make them look differently, so that your users are able to pay special attention to those warning or error messages.

In this article, I will be sharing with you a library which allows you to print colored message in your terminal.

Let’s get started!

The library I am going to introduce called colorama, which is a small and clean library for styling your messages in both Windows, Linux and Mac os.

Prerequisite :

You will need to install this library, so that you will be able to run the following code in this article.

pip install colorama

To start using this library, you will need to import the modules, and call the init() method at the beginning of your script or your class initialization method.

import colorama
from colorama import Fore, Back, Style
colorama.init()

Print colored message with colorama

The init method also accepts some **kwargs to overwrite it’s default behaviors. E.g. by default, the style will not be reset back after printing out a message,  and the subsequent messages will be following the same styles. You can pass in autoreset = true to the init method, so that the style will be reset after each printing statement.

Below are the options you can use when formatting the font, background and style.

Fore: BLACK, RED, GREEN, YELLOW, BLUE, MAGENTA, CYAN, WHITE, RESET.
Back: BLACK, RED, GREEN, YELLOW, BLUE, MAGENTA, CYAN, WHITE, RESET.
Style: DIM, NORMAL, BRIGHT, RESET_ALL

To use it in your message, you can do as per below to wrap your messages with the styles:

print(Fore.CYAN + "Cyan messages will be printed out just for info only" + Style.RESET_ALL)
print(Fore.RED + "Red messages are meant to be to warning or error" + Style.RESET_ALL)
print(Fore.YELLOW + Back.GREEN +  "Yellow messages are debugging info" + Style.RESET_ALL)

This is how it would look like in your terminal:

Python printed colored message with colorama

As I mentioned earlier, if you don’t set the autoreset to true, you will need to reset the style at the end of your each message, so that different message applies different styles.

What if you want to apply the styles when asking user’s input ? Let’s see an example:

print(Fore.YELLOW)
choice = input("Enter YES to confrim:")
print(Style.RESET_ALL)
if str.upper(choice) in ["YES",'Y']:
    print(Fore.GREEN + "You have just confirmed to proceed." + Style.RESET_ALL)
else:
    print(Fore.RED + "You did not enter yes, let's stop here" + Style.RESET_ALL)

By wrapping the input inside Fore.YELLOW and Style.RESET_ALL, whatever output messages from your script or user entry, the same style will be applied.

Let’s put all the above into a script and run it in the terminal to check how it looks like.

Python printed colored message with colorama

Yes, that’s exactly what we want to achieve! Now you can wrap your printing statement into a method e.g.: print_colored_message, so that you do not need to repeat the code everywhere.

As per always, please share if you have any comments or questions.

 

python read and write json file

Read and write json file in python

Json file format is commonly used in most of the programming languages to store data or exchange the data between back end and front end, or between different applications and systems. In this article, I will be explaining how to read and write json file in python programming language.

Read from a JSON file

Python has a json module which makes the read and write json pretty easy. First, let’s assume we have the below example.json file to be read.

{
"link": "www.codeforests.com",
"name": "ken", 
"member": true, 
"hobbies": ["jogging", "watching movie"]
}

To read the file, we can simply use the load method and pass in the file descriptor.

example = json.load(open("example.json"))

Now you can access the example dictionary for the data, e.g.

print(config["hobbies"])

The output would be :

['jogging', 'watching movie']

Write into JSON file

Let’s continue to use the previous example, and try to add one more hobby into the hobbies. Then save the json object into a file.

This time, you can use the json.dump and pass in the file descriptor to be written to:

example["hobbies"].append("badminton")
with open("example.json", "w") as f:
    json.dump(example, f)

If you look at the json documentation, there are two more methods : json.loads and json.dumps. The main difference of this two methods vs json.load & json.dumps is that the loads and dumps take the str representation of the json object. e.g.:

obj = json.loads('{"json":"obj"}')
print(obj)
print(json.dumps({"json":"obj"}))

 

How to read and write configuration (.ini) file in python

There are several file formats you can use for your configuration file, the most commonly used format are .ini, .json and .yaml. In this article, I will sharing with you how to read/write your configurations in the .ini file formats.

Read .ini file

Below is a example of the ini file, you can define the sections (e.g. [LOGIN]) as much as you want to separate the different configuration info.

[LOGIN]
user = admin
#Please change to your real password
password = admin

[SERVER]
host = 192.168.0.1
port = 8088

In python, there is already a module configparser to read an parse the information from the ini file int dictionary objects. Assume you have saved above as config.ini file into your current folder, you can use the below lines of code to read.

import configparser

config = configparser.ConfigParser()		
config.read("config.ini")
login = config['LOGIN']
server = config['SERVER']

You can assign each of the sections into a separate dictionary for easier accessing the values. The output should be same as below:

codeforests read ini file

Note that the line starting with # symbol (or ; ) will be taken as comment line and omitted when parsing the keys and values.

Also all the values are taken as string, so you will need to do your own data type conversion after you read it.

Write .ini file

Now let’s see how we can write to an ini file.

You will still need this configparser library, and the idea is that you need to set the keys and values into the configparser object and then save it into a file.

config = configparser.ConfigParser()
if not config.has_section("INFO"):
    config.add_section("INFO")
    config.set("INFO", "link", "www.codeforests.com")
    config.set("INFO", "name", "ken")

with open("example.ini", 'w') as configfile:
    config.write(configfile)

And this would create the example.ini file with below content:

[INFO]
link = www.codeforests.com
name = ken

I have created another two separate articles to cover the .json and .yaml format, please have a look if you are interested.

As per always, welcome any comments or questions.