Topic 3 - Session 3 - MTA Intro Course

Question 1

To open a file in python, you need to specify two arguments, what are they?

Answer 1

1. The file to be opened

2. The mode, i.e. read, write, append or binary.

Question 2

See the example code below. Do you have to supply arguments to close a file?

workFile.close()

Answer 2

No

Question 3

If you opened a file and wanted to read one line and assign it to a variable, what code would you use?

Answer 3

firstLine = workFile.readline()

Question 4

Explain what is happening in the following code example

writeFile = open(‘log.txt’, ‘w’)
toLog = input(“Enter some text”)
writeFile.write(toLog)
writeFile.close()

Answer 4

1. The first line is opening the file in write mode.
2. User is prompted to enter some text.
3. The data stored in the variable is written to the file.
4. The file is closed.

Question 5

What would happen if you had entered some text and ran this section of code again?

writeFile = open(‘log.txt’, ‘w’)
toLog = input(“Enter some text”)
writeFile.write(toLog)
writeFile.close()

Answer 5

It would overwrite existing text.

Question 6

If you need to create a new file on a system, what python library would you need?

Answer 6

import os

Question 7

Explain what is happening with this following code

import os
if os.path.isfile('log.txt'):
   writeFile = open('log.txt', 'a')
else
   writeFile = open('log.txt', 'w')

Answer 7

1. The required library is first imported.
2. The if statement will check to see if the file exists. If it does, it will open it in append mode.
3. Else, it will create the file and open in write mode.

Question 8

Using the import os library, how would you delete a file?

Answer 8

os.remove(‘log_old.txt’)

Question 9

When working with file, what is a better method of closing the file without using the close() function.

Answer 9

with open (‘log.txt’, ‘w’) as writeFile:

Question 10

The following code is trying to print strings and integers. Instead of using type casting, what alternative could be used?

print(“We have “ + widgets + “ in stock.”)

Answer 10

Use formatted text instead.

Example:
The letter ‘f’ is added in front of quotation marks to indicate the presence of formatted text.

print(f”We have {widgets} widgets in stock.”)

Question 11

When working with files, what is the purpose of the ‘with’ statement.

Answer 11

This statement ensures a file is properly closed.