Answer: In Python, you can use a for loop with readlines() method to read the file line by line.
It is necessary to read a file line by line as it has to be interpreted for proper utilization and accessibility. You can also use for loop method that reads all the lines in the file at once and returns them as a list. In this article, we can explore the various methods and techniques.
Table of Contents:
Before we begin with the methods to read a file line-by-line in Python, we need to create a file which we’ll use later in this article to read its contents.
Hello!!
This is Intellipaat
Have a good day
Now, save this content in a file and name it as file.txt.
Methods to Read a File line-by-line into a List in Python
Python provides multiple methods in its built-in library to perform various file-handling operations. Following are some of these methods that can be used to read a file line-by-line in Python:
Method 1: Using readlines() Method to Read a File Line by Line in Python
The readlines() method in Python reads all the lines from a file and returns them as a list of strings. Each element in the list corresponds to a line in the file, including the newline characters (\n).
Example:
Output:
Explanation: We can open the file with open ‘file.txt’, ‘r’ it opens the file file.txt in read mode.file.readlines() reads all lines from the file and returns them as a list of strings. Each string represents a line in the file, including newline characters (\n). The list comprehension line.strip() removes the newline characters (\n) from the end of each line
Method 2: Using a For Loop to Read a File Line by Line in Python
Reading a text file using a for loop will iterate every line in a text file. In Python, this is commonly done by opening the file, using a for loop to read each line, and then performing operations on each line.
Example:
Output:
Explanation: The for loop iterates over each line in the file, and line.strip() removes any unnecessary whitespace from the beginning and end of each line before displaying the file’s content.
Method 3: Using read() Method to Read a File Line by Line in Python
The read() method in Python will help you read the entire content of the file at once into a single string. This method allows you to access the whole content of the file, which can be useful for smaller files where you need to process all the data at once.
Example:
Output in the file.txt will be,
Explanation: The file.read() method reads the entire content of the file and stores it in the content. After reading, the entire text from the file will be available as a single string, including any newlines or spaces.
Method 4: List Comprehension Method to Read a File Line by Line in Python
The list comprehension method is also used to read the file line-by-line in a list. This method combines iterating and storing the result into a new list in one line.
Example:
Output:
Method 5: Using mmap Module to Read a File Line by Line in Python
The mmap (memory-mapped file) module in Python provides memory-mapped file objects, allowing you to access the contents of a file in memory, just as if it were part of the memory address space. This is useful for efficiently reading and manipulating large files, particularly when you don’t want to load the entire file into memory at once.
Example:
Output:
Explanation: Each line from the file is printed separately, confirming that the file was read line-by-line into a list.
Conclusion
Reading files in Python can be done using various methods, such as ‘readlines()’, loops, or even memory mapping with the ‘mmap’ module. Each approach serves different use cases, whether you need to read a file line-by-line or efficiently handle large files. Using the methods explained above you can depend on factors like file size and the specific task you’re working on.