Python Tutorial

Python Variable

Python Operators

Python Sequence

Python String

Python Flow Control

Python Functions

Python Class and Object

Python Class Members (properties and methods)

Python Exception Handling

Python Modules

Python File Operations (I/O)

Python readline() and readlines() functions: read files line by line

In Python, you can use the readline() and readlines() functions to read files line by line.

`readline()` function

The readline() function reads a single line from a file and returns it as a string. Each time you call readline(), it will return the next line in the file.

Example usage:

with open('file.txt', 'r') as f:
    line1 = f.readline()
    line2 = f.readline()
    print(line1)
    print(line2)

This code opens a file named file.txt in text mode, reads the first two lines of the file using f.readline(), and then prints the resulting strings.

`readlines()` function

The readlines() function reads all the lines in a file and returns them as a list of strings. Each string in the list represents a single line from the file.

Example usage:

with open('file.txt', 'r') as f:
    lines = f.readlines()
    print(lines)

This code opens a file named file.txt in text mode, reads all the lines in the file using f.readlines(), and then prints the resulting list of strings.

You can also use a loop to iterate over the lines in the file, which can be useful if you want to process the lines one at a time:

with open('file.txt', 'r') as f:
    for line in f:
        print(line)

This code opens a file named file.txt in text mode and uses a loop to iterate over the lines in the file. Each time through the loop, it prints the current line.

Note that the readline() and readlines() functions can be memory-intensive if you are reading large files, because they read the entire file into memory at once. In such cases, you may want to consider using the open() function with a for loop to read the file line by line, which is more memory-efficient.

Python readline() function example for reading lines:
- Description: Use the readline() function to read a single line from a file and move the cursor to the next line.
- Code:
```
# Open a file in text mode
with open('example.txt', 'r') as file:
    # Read the first line
    line = file.readline()
    print(line)
```

Reading files line by line with readline() in Python:

Description: Read a file line by line using a loop with the readline() function.

Code:

# Open a file in text mode
with open('example.txt', 'r') as file:
    # Read lines one by one
    line = file.readline()
    while line:
        print(line)
        line = file.readline()

How to use readlines() in Python for file line reading:

Description: Use the readlines() function to read all lines from a file and return them as a list.

Code:

# Open a file in text mode
with open('example.txt', 'r') as file:
    # Read all lines into a list
    lines = file.readlines()
    for line in lines:
        print(line)

Reading specific lines from a file with readline() in Python:

Description: Use readline() in a loop to reach a specific line in a file.

Code:

# Open a file in text mode
with open('example.txt', 'r') as file:
    # Skip lines until reaching the desired line
    for _ in range(5):
        file.readline()

    # Read the desired line
    specific_line = file.readline()
    print(specific_line)

Efficient file line reading using readline() in Python:

Description: Efficiently read lines from a file using a loop with readline() in a try-except block.

Code:

# Open a file in text mode
with open('large_file.txt', 'r') as file:
    try:
        while True:
            line = file.readline()
            if not line:
                break
            # Process the line
            print(line)
    except Exception as e:
        print(f"Error: {e}")

Processing lines from a file with readlines() in Python:

Description: Use readlines() to read all lines into a list and then process the lines as needed.

Code:

# Open a file in text mode
with open('example.txt', 'r') as file:
    # Read all lines into a list
    lines = file.readlines()

    # Process lines
    for line in lines:
        print(line)

Skipping lines while reading a file in Python with readline():

Description: Use readline() in a loop to skip a specified number of lines in a file.

Code:

# Open a file in text mode
with open('example.txt', 'r') as file:
    # Skip the first 3 lines
    for _ in range(3):
        file.readline()

    # Read and process the rest of the lines
    remaining_lines = file.readlines()
    for line in remaining_lines:
        print(line)

Iterating over lines in a file using readline() in Python:

Description: Iterate over lines in a file using a loop with readline() for efficient line-by-line processing.

Code:

# Open a file in text mode
with open('example.txt', 'r') as file:
    # Iterate over lines
    while True:
        line = file.readline()
        if not line:
            break
        # Process the line
        print(line)

Python readline() and readlines() functions: read files line by line

readline() function

readlines() function

`readline()` function

`readlines()` function