Statement
Solution
Python Exercise 7.2: Log Reader
Log files are a common source of data in real-world applications. Write a program that reads a log file called server.log and counts how many lines contain the word "ERROR".
Your program should:
- Create a file named
server.logand write several lines to it, some containing the wordERRORand some that don't. - Open and read the file line by line.
- Count the number of lines that contain the word
"ERROR". - Print the total count of error lines found.
- Use a
try/exceptblock to handle the case where the file does not exist (FileNotFoundError).
Sample Interaction:
Input
Output
(None)
Reading server.log...
Total ERROR lines found: 3
Solution
We first write the log file, then open it for reading and scan each line for the keyword "ERROR", keeping a running counter.
# 1. Create a sample server.log file
log_content = """INFO: Server started successfully
INFO: Connection established from 192.168.1.1
ERROR: Disk space running low
INFO: Request processed in 120ms
ERROR: Database connection timeout
WARNING: Memory usage above 80%
ERROR: Failed to authenticate user
INFO: Backup completed successfully
"""
with open("server.log", "w") as f:
f.write(log_content)
# 2. Read the file and count ERROR lines
try:
error_count = 0
print("Reading server.log...")
with open("server.log", "r") as f:
for line in f:
if "ERROR" in line:
error_count += 1
print(f"Total ERROR lines found: {error_count}")
except FileNotFoundError:
print("Error: server.log file not found.")
Key Concepts:
open("file", "r")opens a file for reading;"w"opens it for writing.- The
withstatement automatically closes the file when the block exits. - Iterating over a file object reads it line by line.
"ERROR" in linechecks if the substring exists anywhere in the line.FileNotFoundErroris raised when Python cannot locate the specified file.
Test Console
Run code to see output...
