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Read File Lines

Zero-dependency Python snippets for reading files line by line using the standard library.

4 snippets available in this sub-category.

Simple

Read file as list of lines

file read lines list

Read all lines from file into a list

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

Notes

  • Each line includes the newline character
  • Returns empty list if file is empty
  • Loads entire file into memory

Read lines without newlines

file read lines splitlines

Read lines and remove newline characters

with open("file.txt", "r") as f:
    lines = f.read().splitlines()
print(lines)

Notes

  • Removes trailing newlines from each line
  • Alternative to readlines() + strip()
  • More memory efficient than readlines()

Complex

Read lines with line numbers

file read lines enumerate generator

Read file with line numbers for debugging or processing

def read_lines_with_numbers(filename):
    """Read file lines with line numbers."""
    with open(filename, "r") as f:
        for line_num, line in enumerate(f, 1):
            yield line_num, line.rstrip()


# Print lines with numbers
for num, line in read_lines_with_numbers("file.txt"):
    print(f"{num:3d}: {line}")

Notes

  • Uses enumerate to get line numbers
  • Starts numbering from 1 (not 0)
  • Strips trailing whitespace
  • Memory efficient for large files

Read lines with filtering

file read lines filter generator

Read lines with custom filtering function

def read_lines_filtered(filename, filter_func=None):
    """Read and filter lines from file."""
    with open(filename, "r") as f:
        for line in f:
            line = line.rstrip()
            if filter_func is None or filter_func(line):
                yield line


# Read only non-empty lines
non_empty = list(read_lines_filtered("file.txt", lambda x: x.strip()))

# Read only lines starting with '#'
comments = list(read_lines_filtered("file.txt", lambda x: x.startswith("#")))

Notes

  • Flexible filtering with custom functions
  • Memory efficient for large files
  • Can filter by any condition
  • Useful for processing log files or config files

🔗 Cross-References

🏷️ Tags

file, read, lines, text, io

📝 Notes

  • Use readlines() to read all lines from a file
  • Returns a list of strings (one per line)
  • Useful for processing line-based data