Final answer:
The read() method is used to read the entire contents of a file in a single operation. It should be used judiciously for large files due to memory consumption. Other methods like readline() and readlines() offer alternative ways of reading files that may be more memory-efficient.
Step-by-step explanation:
The method that reads the entire file contents in a single operation is the read() method. This method is particularly useful when you have a file that you want to work with all at once, as it reads the whole file into memory as a single string. However, it's important to use this method with care, especially with large files, since it can consume a significant amount of memory. Other methods like readline(), which reads a single line from the file, or readlines(), which reads all the lines in a file and returns them as a list, can be more memory-efficient. Using a function with a for loop is helpful if you want to process each line as you read it, which can be more memory-efficient than read() for large files.