Final answer:
The readline() method is the best choice for reading one line of a file into a single string, as it efficiently reads a single line and returns it, including the newline character.
Step-by-step explanation:
When reading a file using the file object in Python, the method best suited for reading one line of the file into a single string is the readline() method. This method reads a single line from the file and returns it as a string, including the newline character at the end. If the end of the file has been reached, readline() will return an empty string. This makes it very efficient for processing a file line by line, as you can easily loop over the lines of the file without loading the entire file into memory.
When reading a file using the file object in Python, the readline() method is best for reading one line of the file into a single string.
For example:
f = open('file.txt', 'r')
line = f.readline()
print(line)
This code will open the file 'file.txt', read the first line, and store it in the variable 'line' as a string.