To solve this problem, we need to create a Python script that searches for a specific string in a given file, reports the line numbers where the string appears, counts occurrences per line, and provides a total count of occurrences. The script should handle common errors (like file not found or permission issues) and offer an option for case-sensitive or case-insensitive search.

Approach

1. Input Handling:

   • Prompt the user for the file path.
   • Prompt for the search string (ensure it's not empty).
   • Ask if the search should be case-sensitive.

2. File Processing:

   • Open the file in read mode (with error handling for common issues like missing files or permission errors).
   • Read the file line by line to avoid memory issues with large files.
   • For each line, check if the search string exists (considering case sensitivity).
   • Count occurrences per line and total occurrences.

3. Output:

   • Print lines where the string is found (with line numbers and occurrence count per line).
   • Print the total number of occurrences or a message if no matches are found.

Solution Code

def search_file():
    # Get file path from user
    file_path = input("Enter the path to the file you want to search: ").strip()

    # Get non-empty search string
    while True:
        search_str = input("Enter the string to search for: ").strip()
        if search_str:
            break
        print("Error: Search string cannot be empty. Please try again.")

    # Case sensitivity option
    case_sensitive = input("Perform case-sensitive search? (y/n): ").strip().lower() == 'y'

    try:
        with open(file_path, 'r', encoding='utf-8') as file:
            line_number = 0
            total_occurrences = 0

            for line in file:
                line_number += 1
                # Adjust for case sensitivity
                if case_sensitive:
                    line_check = line
                    str_check = search_str
                else:
                    line_check = line.lower()
                    str_check = search_str.lower()

                # Check for matches
                if str_check in line_check:
                    count_in_line = line_check.count(str_check)
                    total_occurrences += count_in_line
                    # Print the original line (without trailing newline)
                    print(f"\nLine {line_number}: {line.rstrip()}")
                    print(f"Occurrences in this line: {count_in_line}")

            # Final report
            if total_occurrences == 0:
                print(f"\nNo occurrences of '{search_str}' found in the file.")
            else:
                print(f"\nTotal occurrences of '{search_str}': {total_occurrences}")

    except FileNotFoundError:
        print(f"\nError: File '{file_path}' not found.")
    except PermissionError:
        print(f"\nError: You do not have permission to read '{file_path}'.")
    except UnicodeDecodeError:
        print(f"\nError: The file '{file_path}' is not a text file (binary or unsupported encoding).")
    except Exception as e:
        print(f"\nUnexpected error: {str(e)}")

if __name__ == "__main__":
    search_file()

Explanation

• Input Validation: The script ensures the search string is not empty to avoid invalid searches.
• Case Sensitivity: Users can choose between case-sensitive and case-insensitive searches, making the tool flexible.
• Error Handling: The script catches common errors (file not found, permission issues, non-text files) and provides meaningful messages to the user.
• Efficiency: Reading the file line by line ensures that even large files are processed without excessive memory usage.
• Clear Output: The script prints the exact lines where the string is found, along with line numbers and occurrence counts, making it easy to locate matches.

This script is user-friendly and robust, suitable for both basic and slightly advanced search needs in text files.

作者声明:本文包含人工智能生成内容。