Syntax:
“ file.readline(size) “
The syntax above is used for the readline method in python. The file in the syntax is the file we created (we are specifying the file here). The readline is the function used for reading the lines in the file and the size is an argument used for the size specification of the number. The string will return the data value of that size given. The size argument is optional. The by-default value set is “-1”, which means that all of the lines included in the file will be the resultant factor. The return value is the result that will come out by the reading method from the file given.
The Ways to Perform the Python Readline Loop Method
The following is how we can perform the readline loop method in python. First, create a file and add the data to it. It could be any data we want to work on. We have created the file here named “open python file”, in which we have added the data which we will be using for fetching purposes to implement the readline function in python.
- Executing the readline() method to read the first line.
- Executing readline() method to read file line by line.
- Executing readline() method using size argument.
- Executing the readline() method to read all lines in the file together.
Example # 01: Executing the readline() Method to Read the First Line
In this example, we will be learning how to read the first line using the readline() method in python. For the execution of the method readline, we have to create a text file of any name, in which we want to perform the reading method. Here, the file created name is “open python file”. In the first line of the code, we enter the command for opening the file for the reading purpose using the method of open(). For opening the file, the two parameters are added.
The method of opening () the first parameter is taking the name to enter which we have given to the file. Whereas, the second parameter is for the examination and referring to the file attribute, here we have taken “r”, which is used for the reading in the file we have opened. Then, use the readline() method for printing the read line from the file. For printing, employ the print function in python. After the reading, the function is executed close the file utilizing the close() method.
print (objFile.readline());
objFile.close()
The output shows the first line of the selected file printed successfully. The “C:\” in the output shows that the file we have been working on is in the C folder.
Example # 02: Executing readline() Method to Read File Line by Line
In this instance, we will be looking at how to read the file line by line using the readline() method in python. The readline method generally reads the first line from the file and returns the results. Here, we will be working to make the readline() method read more than one line from the file. The file should be created first. For making the reading efficient and to read more lines the best way is to use the for a loop. The for loop function will keep on rotating and iterating till the line we want the readline() method to read.
Here, we have not declared the number of lines for the reading. So, by default, it will read each line of the file using readline() and print the results. For the output display on the screen make use of the print function in python. Also, do close the file by using the close() method.
for line in myfolder:
print (line)
objFile_size.close()
The display came out to be in the lines by reading the file “open python file.txt” using readline() in python.
Example # 03: Executing readline() Method Using Size Argument
In this example, we will be working on how to read the line by the argument given in size using the readline() method in python. Now here, the size parameter works in a way that it will return the same number of characters. Suppose we enter the argument size as “3” so, it will read the line from the file and will return the characters from 0 to 3 as the output. Here, we have shown the argument size as “2”. Then, use the print function for printing the output. Lastly, close the file by using the close() function.
print (objFile_size.readline(2));
objFile_size.close()
The output displays the two characters from the first line of the file successfully.
Let us take another example where we have taken the size argument as “5”. The reading method in python does not count the wide spaces as a character. We have opened the file and given the parameter as the file name we created already. Then, use the print function for printing and give the argument size in it. Close the file by using the close() function.
print (objFile_size.readline(5));
objFile_size.close()
The output shows the 5 characters displayed by reading the file using the readline method in python with size argument.
Example # 04: Executing the readline() Method to Read All Lines in the File at the Same Time
In this instance, we will be learning how to read all the lines in the file at the same time using the readline() method. There is a special feature of the python function readline() that will read the file and returns the data in the form of a list. We will use the readline function for reading all the lines in the file. First, open the created file with the name saved. Then, use the readline() function for reading the file and use the print function for printing the results on the output screen.
my folder =myfile.readlines()
print (my folder)
objFile_size.close()
Here we can see that the whole file is read and printed in the form of a list with the line number reference.
Conclusion
In this article, we have examined all of the possible ways of using the readline function in python. It is a useful method in terms of fetching the data from the specific file and getting the results. We can do that in many ways such as by a line, character, and also the whole file. We have implemented the readline() method to read the first line, the implementation of the readline() method to read the file line by line, implementation of the readline() method to read all lines in the file at the same time, and also the implementation of the readline() method using size argument.
