Every real-world application reads or writes data. Whether it\u2019s user preferences, logs, or exported reports, file handling is unavoidable. But files can fail \u2014 missing files, permission errors, corrupted data. That\u2019s where exception handling saves you.<\/p>\n\n\n\n
In this post:<\/p>\n\n\n\n
try<\/code>,\u00a0except<\/code>,\u00a0else<\/code>,\u00a0finally<\/code><\/li>\n\n\n\n- Best practices for robust code<\/li>\n<\/ul>\n\n\n\n
\n\n\n\nText Files: The Basics<\/h3>\n\n\n\nWriting to a TXT file<\/h3>\n\n\n\n
python<\/p>\n\n\n\n
with open(\"data.txt\", \"w\") as file:\n file.write(\"Hello, World!\")<\/pre>\n\n\n\nThe with<\/code> statement automatically closes the file. Never use open()<\/code> without with<\/code> in production code.<\/p>\n\n\n\nReading from a TXT file<\/h3>\n\n\n\n
python<\/p>\n\n\n\n
with open(\"data.txt\", \"r\") as file:\n content = file.read()\n print(content)<\/pre>\n\n\n\nModes: \"r\"<\/code> = read, \"w\"<\/code> = write (overwrites), \"a\"<\/code> = append.<\/p>\n\n\n\n
\n\n\n\nJSON Files: Structured Data<\/h3>\n\n\n\n
JSON is the universal language of APIs and config files.<\/p>\n\n\n\n
Writing JSON<\/h3>\n\n\n\n
python<\/p>\n\n\n\n
import json\n\ndata = {\"name\": \"Alice\", \"age\": 30}\nwith open(\"user.json\", \"w\") as file:\n json.dump(data, file, indent=4)<\/pre>\n\n\n\nReading JSON<\/h3>\n\n\n\n
python<\/p>\n\n\n\n
with open(\"user.json\", \"r\") as file:\n data = json.load(file)\n print(data[\"name\"]) # Alice<\/pre>\n\n\n\nAlways use indent<\/code> for readability when writing JSON manually.<\/p>\n\n\n\n
\n\n\n\nCSV Files: Tabular Data<\/h3>\n\n\n\n
CSV (Comma-Separated Values) is everywhere in data exports.<\/p>\n\n\n\n
Reading CSV<\/h3>\n\n\n\n
python<\/p>\n\n\n\n
import csv\n\nwith open(\"employees.csv\", \"r\") as file:\n reader = csv.reader(file)\n for row in reader:\n print(row)<\/pre>\n\n\n\nWriting CSV<\/h3>\n\n\n\n
python<\/p>\n\n\n\n
with open(\"output.csv\", \"w\", newline=\"\") as file:\n writer = csv.writer(file)\n writer.writerow([\"Name\", \"Age\"])\n writer.writerow([\"Bob\", 25])<\/pre>\n\n\n\nnewline=\"\"<\/code> prevents blank lines between rows on Windows.<\/p>\n\n\n\n
\n\n\n\nException Handling: Preventing Crashes<\/h3>\n\n\n\n
Files don’t always exist. Networks fail. JSON gets corrupted.<\/p>\n\n\n\n
Basic try-except<\/code><\/h3>\n\n\n\npython<\/p>\n\n\n\n
try:\n with open(\"missing.txt\", \"r\") as file:\n print(file.read())\nexcept FileNotFoundError:\n print(\"File not found. Creating a new one.\")\n with open(\"missing.txt\", \"w\") as file:\n file.write(\"Default content\")<\/pre>\n\n\n\nMultiple Exceptions<\/h3>\n\n\n\n
python<\/p>\n\n\n\n
try:\n value = int(input(\"Enter number: \"))\n result = 10 \/ value\nexcept ValueError:\n print(\"That's not a number!\")\nexcept ZeroDivisionError:\n print(\"Cannot divide by zero!\")<\/pre>\n\n\n\nelse<\/code> and finally<\/code><\/h3>\n\n\n\n\nelse<\/code>: Runs if no exception occurred.<\/li>\n\n\n\nfinally<\/code>: Always runs (cleanup code).<\/li>\n<\/ul>\n\n\n\npython<\/p>\n\n\n\n
try:\n file = open(\"log.txt\", \"r\")\nexcept FileNotFoundError:\n print(\"File missing\")\nelse:\n print(\"File read successfully\")\nfinally:\n print(\"Execution complete\")<\/pre>\n\n\n\n
\n\n\n\nBest Practices<\/h3>\n\n\n\n\n- Catch specific exceptions<\/strong>\u00a0\u2014 never use bare\u00a0
except:<\/code>.<\/li>\n\n\n\n- Use\u00a0
with<\/code>\u00a0for files<\/strong>\u00a0\u2014 automatic closing.<\/li>\n\n\n\n- Log exceptions<\/strong>\u00a0in production apps instead of just printing.<\/li>\n\n\n\n
- Validate JSON<\/strong>\u00a0before parsing.<\/li>\n<\/ol>\n\n\n\n
\n\n\n\nSummary<\/h3>\n\n\n\nFile Type<\/th> Read Method<\/th> Write Method<\/th><\/tr><\/thead> TXT<\/td> open().read()<\/code><\/td>open().write()<\/code><\/td><\/tr>JSON<\/td> json.load()<\/code><\/td>json.dump()<\/code><\/td><\/tr>CSV<\/td> csv.reader()<\/code><\/td>csv.writer()<\/code><\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n<\/p>\n","protected":false},"excerpt":{"rendered":"
Introduction Every real-world application reads or writes data. Whether it\u2019s user preferences, logs, or exported reports, file handling is unavoidable. But files can fail \u2014 missing files, permission errors, corrupted data. That\u2019s where exception handling saves you. In this post: Text Files: The Basics Writing to a TXT file python with open(“data.txt”, “w”) as file: […]<\/p>\n","protected":false},"author":69,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[1],"tags":[],"class_list":["post-3473","post","type-post","status-publish","format-standard","hentry","category-support"],"_links":{"self":[{"href":"https:\/\/www.mhtechin.com\/support\/wp-json\/wp\/v2\/posts\/3473","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.mhtechin.com\/support\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.mhtechin.com\/support\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.mhtechin.com\/support\/wp-json\/wp\/v2\/users\/69"}],"replies":[{"embeddable":true,"href":"https:\/\/www.mhtechin.com\/support\/wp-json\/wp\/v2\/comments?post=3473"}],"version-history":[{"count":2,"href":"https:\/\/www.mhtechin.com\/support\/wp-json\/wp\/v2\/posts\/3473\/revisions"}],"predecessor-version":[{"id":3485,"href":"https:\/\/www.mhtechin.com\/support\/wp-json\/wp\/v2\/posts\/3473\/revisions\/3485"}],"wp:attachment":[{"href":"https:\/\/www.mhtechin.com\/support\/wp-json\/wp\/v2\/media?parent=3473"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.mhtechin.com\/support\/wp-json\/wp\/v2\/categories?post=3473"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.mhtechin.com\/support\/wp-json\/wp\/v2\/tags?post=3473"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}