Chapter 12: Problem 38

The ___ mode flag causes an offset to be calculated from the end of a file.

Short Answer

Expert verified

Answer: The 'os.SEEK_END' mode flag, used in combination with the 'seek()' method, causes an offset to be calculated from the end of a file. To use it, open the file, and then apply the 'seek()' method with the desired offset and 'os.SEEK_END', like this: `file.seek(-N, os.SEEK_END)`. Replace 'N' with the number of positions you want to offset from the end of the file, using a negative integer to move backwards in the file.

Step by step solution

Identifying the correct mode flag

The correct mode flag is 'seek' in combination with 'os.SEEK_END'. The 'seek()' method is used to change the current file position. The 'os.SEEK_END' mode flag makes the offset to be calculated from the end of the file.

Explaining how to use the mode flag

To use the 'seek()' method with 'os.SEEK_END', you need to open the file in a mode that allows you to read or write: 1. First, import the 'os' module: `import os` 2. Open the file using the `open()` function: `with open('filename.txt', 'rb' or 'r' or 'wb' or 'w' or 'ab' or 'a') as file:` 3. Then, use the `seek()` method with the desired offset and 'os.SEEK_END': `file.seek(-N, os.SEEK_END)` Replace 'N' with the number of positions you want to offset from the end of the file. It must be a negative integer if you want to move backwards in the file.

Demonstrate with an example

Suppose you have a text file named 'example.txt', and you want to read the last 5 characters of the file. You can use the 'seek()' method with 'os.SEEK_END' as follows: ```python import os with open('example.txt', 'rb') as file: file.seek(-5, os.SEEK_END) data = file.read() print(data.decode()) ``` This code snippet will print the last 5 characters of the file.

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The ___ mode flag causes an offset to be calculated from the end of a file.

Short Answer

Step by step solution

Identifying the correct mode flag

Explaining how to use the mode flag

Demonstrate with an example

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