Why data logging matters for IoT in Raspberry Pi - Test Your Understanding

Practice - 5 Tasks

1fill in blank

easy

Complete the code to start logging sensor data to a file.

Raspberry Pi

with open('sensor_data.txt', '[1]') as file:
    file.write('Temperature: 22C\n')

Drag options to blanks, or click blank then click option'

Aa

Bx

Cw

Dr

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'w' erases existing data.

Using 'r' opens file for reading only.

Using 'a' opens the file in append mode, so new data is added without erasing existing data.

2fill in blank

medium

Complete the code to read the last line of the log file.

Raspberry Pi

with open('sensor_data.txt', 'r') as file:
    lines = file.readlines()
    last_line = lines[1]

Drag options to blanks, or click blank then click option'

A[:1]

B[0]

C[1]

D[-1]

Attempts:

3 left

💡 Hint

Common Mistakes

Using [0] gets the first line, not the last.

Using [:1] returns a list with the first line.

Using [-1] gets the last item from the list of lines.

3fill in blank

hard

Fix the error in the code to log data with a timestamp.

Raspberry Pi

import datetime
now = datetime.datetime.now()
with open('log.txt', 'a') as file:
    file.write(f"[1] - Sensor reading\n")

Drag options to blanks, or click blank then click option'

Adatetime.now()

Bnow.time()

Cnow.strftime('%Y-%m-%d %H:%M:%S')

Ddatetime.datetime()

Attempts:

3 left

💡 Hint

Common Mistakes

Using datetime.now() without import or formatting causes error.

Using now.time() gives only time, missing date.

Using now.strftime formats the datetime object into a readable string for logging.

4fill in blank

hard

Fill both blanks to create a dictionary logging temperature readings above 25 degrees.

Raspberry Pi

log = {sensor[1]: reading for sensor, reading in readings.items() if reading [2] 25}

Drag options to blanks, or click blank then click option'

A.upper()

B>

C<

D.lower()

Attempts:

3 left

💡 Hint

Common Mistakes

Using '<' filters wrong readings.

Not converting sensor names to uppercase.

We convert sensor names to uppercase and filter readings greater than 25.

5fill in blank

hard

Fill all three blanks to filter and log sensors with readings below 20 and convert sensor names to lowercase.

Raspberry Pi

filtered_log = [1]: [2] for [3], value in sensor_data.items() if value < 20}

Drag options to blanks, or click blank then click option'

Asensor.lower()

Bvalue

Csensor

Dreading

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'reading' instead of 'sensor' as loop variable.

Not converting sensor names to lowercase.

We use sensor.lower() as keys, value as values, and sensor as the loop variable.

Practice

1. Why is data logging important for IoT devices like Raspberry Pi sensors?

easy

A. It automatically updates the device software.

B. It makes the device run faster instantly.

C. It reduces the power consumption of the device.

D. It helps track device activity and detect problems over time.

Solution

1. Step 1: Understand the purpose of data logging

   Data logging records information from devices continuously or at intervals.

2. Step 2: Identify benefits for IoT devices

   This recorded data helps track device activity and find issues over time.

3. Final Answer:

   It helps track device activity and detect problems over time. -> Option D

4. Quick Check:

   Data logging = track and detect problems [OK]

Hint: Data logging = tracking device info over time [OK]

Common Mistakes:

• Confusing logging with speeding up device
• Thinking logging reduces power use
• Assuming logging updates software automatically

2. Which command correctly appends sensor data to a log file on Raspberry Pi?

easy

A. echo "temp=25" >> sensor.log

B. echo "temp=25" > sensor.log

C. cat sensor.log >> echo "temp=25"

D. echo "temp=25" | sensor.log

Solution

1. Step 1: Understand shell redirection operators

   '>>' appends text to a file, '>' overwrites the file.

2. Step 2: Choose the command that appends data

   Only 'echo "temp=25" >> sensor.log' appends without erasing existing data.

3. Final Answer:

   echo "temp=25" >> sensor.log -> Option A

4. Quick Check:

   Append with >> operator [OK]

Hint: Use >> to add data without erasing file [OK]

Common Mistakes:

• Using > which overwrites the file
• Misusing cat or pipe commands incorrectly
• Confusing append and overwrite operators

3. Given this Python code on Raspberry Pi, what will be the content of 'log.txt' after running it twice?

with open('log.txt', 'a') as f:
    f.write('Temperature: 22\n')

medium

A. Temperature: 22

B. Temperature: 22\n

C. Temperature: 22\nTemperature: 22\n

D. Error: file not found

Solution

1. Step 1: Understand file mode 'a' in Python

   Mode 'a' appends text to the file without deleting existing content.

2. Step 2: Analyze running code twice

   Each run adds 'Temperature: 22\n' once, so two runs add it twice.

3. Final Answer:

   Temperature: 22\nTemperature: 22\n -> Option C

4. Quick Check:

   Append mode adds lines each run [OK]

Hint: Mode 'a' appends, so repeated runs add lines [OK]

Common Mistakes:

• Thinking 'a' overwrites file
• Ignoring newline characters
• Expecting error when file exists

4. This Python code is meant to log sensor data but fails to save anything. What is the error?

f = open('data.log', 'w')
f.write('Humidity: 45%')
f.close()

medium

A. The file mode 'w' erases previous logs each run.

B. Missing newline character causes no data saved.

C. File is not closed properly.

D. The write method syntax is incorrect.

Solution

1. Step 1: Understand file mode 'w' behavior

   Mode 'w' overwrites the file, erasing previous logs each time.

2. Step 2: Identify why logs seem missing

   Each run deletes old data, so only last run's data remains, seeming like no logs.

3. Final Answer:

   The file mode 'w' erases previous logs each run. -> Option A

4. Quick Check:

   'w' mode overwrites file [OK]

Hint: Use 'a' mode to keep old logs, not 'w' [OK]

Common Mistakes:

• Thinking missing newline stops saving
• Assuming file not closed causes no save
• Believing write syntax is wrong

5. You want to log temperature and humidity every minute on a Raspberry Pi and keep logs for a week. Which approach best supports this goal?

hard

A. Overwrite a single log file every minute with new data only.

B. Use a Python script appending data to a daily log file and rotate files weekly.

C. Store data only in memory without saving to disk.

D. Log data once and delete logs after one hour.

Solution

1. Step 1: Understand logging frequency and retention needs

   Logging every minute generates many entries; keeping a week requires file management.

2. Step 2: Choose a method that appends and rotates logs

   Appending to daily files and rotating weekly keeps data organized and manageable.

3. Final Answer:

   Use a Python script appending data to a daily log file and rotate files weekly. -> Option B

4. Quick Check:

   Append + rotate files = best for long-term logs [OK]

Hint: Append data daily and rotate files weekly [OK]

Common Mistakes:

• Overwriting logs loses past data
• Not saving data to disk risks loss
• Deleting logs too soon loses history