{"id":2749,"date":"2015-03-24T12:15:35","date_gmt":"2015-03-24T10:15:35","guid":{"rendered":"http:\/\/www.webcodegeeks.com\/?p=2749"},"modified":"2015-03-18T10:22:07","modified_gmt":"2015-03-18T08:22:07","slug":"python-streaming-appending-file","status":"publish","type":"post","link":"https:\/\/www.webcodegeeks.com\/python\/python-streaming-appending-file\/","title":{"rendered":"Python: Streaming\/Appending to a file"},"content":{"rendered":"<p>I\u2019ve been playing around with Twitter\u2019s API (via the <a href=\"https:\/\/github.com\/tweepy\/tweepy\">tweepy<\/a> library) and due to the rate limiting it imposes I wanted to stream results to a CSV file rather than waiting until my whole program had finished.<\/p>\n<p>I wrote the following program to simulate what I was trying to do:<br \/>\n&nbsp;<br \/>\n&nbsp;<br \/>\n&nbsp;<br \/>\n&nbsp;<br \/>\n&nbsp;<br \/>\n&nbsp;<\/p>\n<pre class=\"brush: python; title: ; notranslate\" title=\"\">import csv\r\nimport time\r\n\r\nwith open('rows.csv', 'a') as file:\r\n    writer = csv.writer(file, delimiter = ',')\r\n\r\n    end = time.time() + 10\r\n    while True:\r\n        if time.time() &gt; end:\r\n            break\r\n        else:\r\n            writer.writerow(&#x5B;'mark', '123'])\r\n            time.sleep(1)<\/pre>\n<p>The program will run for 10 seconds and append one line to \u2018rows.csv\u2019 once a second. Although I have used the \u2018a\u2019 flag in my call to \u2018open\u2019 if I poll that file before the 10 seconds is up it\u2019s empty:<\/p>\n<pre class=\"brush: bash; title: ; notranslate\" title=\"\">$ date &amp;&amp; wc -l rows.csv\r\nMon  9 Mar 2015 22:54:27 GMT\r\n       0 rows.csv\r\n\r\n$ date &amp;&amp; wc -l rows.csv\r\nMon  9 Mar 2015 22:54:31 GMT\r\n       0 rows.csv\r\n\r\n$ date &amp;&amp; wc -l rows.csv\r\nMon  9 Mar 2015 22:54:34 GMT\r\n       0 rows.csv\r\n\r\n$ date &amp;&amp; wc -l rows.csv\r\nMon  9 Mar 2015 22:54:43 GMT\r\n      10 rows.csv<\/pre>\n<p>I thought the flushing of the file was completely controlled by the with block but lucky for me there\u2019s actually a <cite><a href=\"https:\/\/docs.python.org\/2\/library\/io.html#io.IOBase.flush\">flush()<\/a><\/cite> function which allows me to force writes to the file whenever I want.<\/p>\n<p>Here\u2019s the new and improved sample program:<\/p>\n<pre class=\"brush: python; title: ; notranslate\" title=\"\">import csv\r\nimport time\r\n\r\nwith open('rows.csv', 'a') as file:\r\n    writer = csv.writer(file, delimiter = ',')\r\n\r\n    end = time.time() + 10\r\n    while True:\r\n        if time.time() &gt; end:\r\n            break\r\n        else:\r\n            writer.writerow(&#x5B;'mark', '123'])\r\n            time.sleep(1)\r\n            file.flush()<\/pre>\n<p>And if we poll the file while the program\u2019s running:<\/p>\n<pre class=\"brush: python; title: ; notranslate\" title=\"\">$ date &amp;&amp; wc -l rows.csv\r\nMon  9 Mar 2015 22:57:36 GMT\r\n      14 rows.csv\r\n\r\n$ date &amp;&amp; wc -l rows.csv\r\nMon  9 Mar 2015 22:57:37 GMT\r\n      15 rows.csv\r\n\r\n$ date &amp;&amp; wc -l rows.csv\r\nMon  9 Mar 2015 22:57:40 GMT\r\n      18 rows.csv\r\n\r\n$ date &amp;&amp; wc -l rows.csv\r\nMon  9 Mar 2015 22:57:45 GMT\r\n      20 rows.csv<\/pre>\n<p>Much easier than I expected \u2013 I \u2665 python!<\/p>\n<div class=\"attribution\">\n<table>\n<tbody>\n<tr>\n<td><span class=\"reference\">Reference: <\/span><\/td>\n<td><a href=\"http:\/\/www.markhneedham.com\/blog\/2015\/03\/09\/python-streamingappending-to-a-file\/\">Python: Streaming\/Appending to a file at Mark Needham<\/a> from our <a href=\"http:\/\/www.webcodegeeks.com\/wcg\/\">WCG partner<\/a> Mark Needham at the <a href=\"http:\/\/www.markhneedham.com\/blog\/\">Mark Needham Blog<\/a> blog.<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/div>\n","protected":false},"excerpt":{"rendered":"<p>I\u2019ve been playing around with Twitter\u2019s API (via the tweepy library) and due to the rate limiting it imposes I wanted to stream results to a CSV file rather than waiting until my whole program had finished. I wrote the following program to simulate what I was trying to do: &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &hellip;<\/p>\n","protected":false},"author":48,"featured_media":1651,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[53],"tags":[],"class_list":["post-2749","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-python"],"yoast_head":"<!-- This site is optimized with the Yoast SEO plugin v26.5 - https:\/\/yoast.com\/wordpress\/plugins\/seo\/ -->\n<title>Python: Streaming\/Appending to a file - Web Code Geeks - 2026<\/title>\n<meta name=\"description\" content=\"I\u2019ve been playing around with Twitter\u2019s API (via the tweepy library) and due to the rate limiting it imposes I wanted to stream results to a CSV file\" \/>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/www.webcodegeeks.com\/python\/python-streaming-appending-file\/\" \/>\n<meta property=\"og:locale\" content=\"en_US\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"Python: Streaming\/Appending to a file - 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