Python File Input and Output 5

Question 1

What does json.dump(obj, fp) do versus json.dumps(obj)?

Accepted Answer

dump() writes to a file object; dumps() returns a string

Answer

json.dump() serializes obj and writes directly to a file-like object fp, while json.dumps() returns the JSON string.

Question 2

Which flag in open() prevents Windows from translating '
' to '
' on write?

Accepted Answer

newline=''

Answer

Passing newline='' disables universal newline translation so Python writes exactly the characters you provide without CR+LF conversion.

Question 3

What does os.walk() yield for each directory it visits?

Accepted Answer

A tuple of (dirpath, dirnames, filenames)

Answer

os.walk() yields a 3-tuple (dirpath, dirnames, filenames) for each directory in the tree rooted at the given path.

Question 4

What is the effect of opening a file with mode 'w+' when the file already exists?

Accepted Answer

It truncates the file to zero length then allows reading and writing

Answer

'w+' opens the file for reading and writing but first truncates it to zero bytes, destroying any prior content.

Question 5

How do you read exactly 10 bytes from a binary file?

Accepted Answer

file.read(10)

Answer

file.read(size) reads and returns up to size bytes; in binary mode this returns a bytes object of at most 10 bytes.

Python Practice Test