blocks|key|1315023|text|with+open('document.csv','a')+as+fd:
++++fd.write(myCsvRow)|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|1315024|使用'a'参数打开文件允许您附加到文件的末尾，而不是简单地覆盖现有内容。试试看。|unstyled|offset|length|style|CODE|1315025|entityMap^0|0|2|3|0^^$0|@$1|2|3|4|5|6|7|M|8|@]|9|@]|A|$B|C]]|$1|D|3|E|5|F|7|N|8|@$G|O|H|P|I|J]]|9|@]|A|$]]|$1|K|3|-4|5|F|7|Q|8|@]|9|@]|A|$]]]|L|$]]

<pre><code>with open('document.csv','a') as fd:
 fd.write(myCsvRow)
</code></pre>

Opening a file with the <code>'a'</code> parameter allows you to append to the end of the file instead of simply overwriting the existing content. Try that.

blocks|key|1315048|text|我更喜欢这种解决方案，使用标准库中的csv模块和with语句，以避免使文件处于打开状态。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1315049|关键的一点是在打开文件时使用'a'作为附加。|1315050|import+csv+++
fields=['first','second','third']
with+open(r'name',+'a')+as+f:
++++writer+=+csv.writer(f)
++++writer.writerow(fields)|code-block|syntax|javascript|1315051|如果你使用的是Python+2.7，你可能会在Windows中遇到多余的新行。您可以尝试使用'ab'而不是'a'来避免它们，然而，这会导致您在Python3.6中使用TypeError:+a+bytes-like+object+is+required,+not+'str'+in+python+and+CSV。按照Natacha的建议，添加newline=''将导致a+backward+incompatibility+between+Python+2+and+3。|1315052|entityMap|0|LINK|mutability|MUTABLE|url|https://docs.python.org/2/library/csv.html?highlight=csv#module-csv|1|https://docs.python.org/2/reference/compound_stmts.html#the-with-statement|2|https://stackoverflow.com/questions/34283178/typeerror-a-bytes-like-object-is-required-not-str-in-python-and-csv|3|https://stackoverflow.com/questions/56206233/python-2-and-3-csv-module-text-binary-mode-backwards-compatibility^0|I|3|O|4|I|3|0|O|4|1|0|E|3|0|0|1A|4|1H|3|4Q|A|2B|1Z|2|53|1D|3|0^^$0|@$1|2|3|4|5|6|7|12|8|@$9|13|A|14|B|C]|$9|15|A|16|B|C]]|D|@$9|17|A|18|1|19]|$9|1A|A|1B|1|1C]]|E|$]]|$1|F|3|G|5|6|7|1D|8|@$9|1E|A|1F|B|C]]|D|@]|E|$]]|$1|H|3|I|5|J|7|1G|8|@]|D|@]|E|$K|L]]|$1|M|3|N|5|6|7|1H|8|@$9|1I|A|1J|B|C]|$9|1K|A|1L|B|C]|$9|1M|A|1N|B|C]]|D|@$9|1O|A|1P|1|1Q]|$9|1R|A|1S|1|1T]]|E|$]]|$1|O|3|-4|5|6|7|1U|8|@]|D|@]|E|$]]]|P|$Q|$5|R|S|T|E|$U|V]]|W|$5|R|S|T|E|$U|X]]|Y|$5|R|S|T|E|$U|Z]]|10|$5|R|S|T|E|$U|11]]]]

I prefer this solution using the <a href="https://docs.python.org/2/library/csv.html?highlight=csv#module-csv" rel="noreferrer"><code>csv</code></a> module from the standard library and the <a href="https://docs.python.org/2/reference/compound_stmts.html#the-with-statement" rel="noreferrer"><code>with</code></a> statement to avoid leaving the file open.

The key point is using <code>'a'</code> for appending when you open the file.

<pre><code>import csv 
fields=['first','second','third']
with open(r'name', 'a') as f:
 writer = csv.writer(f)
 writer.writerow(fields)
</code></pre>

If you are using Python 2.7 you may experience superfluous new lines in Windows. You can try to avoid them using <code>'ab'</code> instead of <code>'a'</code> this will, however, cause you <a href="https://stackoverflow.com/questions/34283178/typeerror-a-bytes-like-object-is-required-not-str-in-python-and-csv">TypeError: a bytes-like object is required, not &#39;str&#39; in python and CSV</a> in Python 3.6. Adding the <code>newline=''</code>, as Natacha suggests, will cause you <a href="https://stackoverflow.com/questions/56206233/python-2-and-3-csv-module-text-binary-mode-backwards-compatibility">a backward incompatibility between Python 2 and 3</a>.

blocks|key|1100088|text|#+I+like+using+the+codecs+opening+in+a+with+
field_names+=+['latitude',+'longitude',+'date',+'user',+'text']
with+codecs.open(filename,"ab",+encoding='utf-8')+as+logfile:
++++logger+=+csv.DictWriter(logfile,+fieldnames=field_names)
++++logger.writeheader()

#+some+more+code+stuff+

++++for+video+in+aList:
++++++++video_result+=+{}+++++++++++++++++++++++++++++++++++++
++++++++video_result['date']+=+video['snippet']['publishedAt']
++++++++video_result['user']+=+video['id']
++++++++video_result['text']+=+video['snippet']['description'].encode('utf8')
++++++++logger.writerow(video_result)+|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|1100089|unstyled|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|G|8|@]|9|@]|A|$B|C]]|$1|D|3|-4|5|E|7|H|8|@]|9|@]|A|$]]]|F|$]]

<pre><code># I like using the codecs opening in a with 
field_names = ['latitude', 'longitude', 'date', 'user', 'text']
with codecs.open(filename,"ab", encoding='utf-8') as logfile:
 logger = csv.DictWriter(logfile, fieldnames=field_names)
 logger.writeheader()

# some more code stuff 

 for video in aList:
 video_result = {} 
 video_result['date'] = video['snippet']['publishedAt']
 video_result['user'] = video['id']
 video_result['text'] = video['snippet']['description'].encode('utf8')
 logger.writerow(video_result) 
</code></pre>

blocks|key|1315111|text|如果文件存在且包含数据，则可以自动为csv.DictWriter生成fieldname参数：|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1315112|#+read+header+automatically
with+open(myFile,+"r")+as+f:
++++reader+=+csv.reader(f)
++++for+header+in+reader:
++++++++break

#+add+row+to+CSV+file
with+open(myFile,+"a",+newline='')+as+f:
++++writer+=+csv.DictWriter(f,+fieldnames=header)
++++writer.writerow(myDict)|code-block|syntax|javascript|1315113|entityMap^0|I|E|Y|9|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@$9|N|A|O|B|C]|$9|P|A|Q|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|R|8|@]|D|@]|E|$I|J]]|$1|K|3|-4|5|6|7|S|8|@]|D|@]|E|$]]]|L|$]]

If the file exists and contains data, then it is possible to generate the <code>fieldname</code> parameter for <code>csv.DictWriter</code> automatically:

<pre><code># read header automatically
with open(myFile, "r") as f:
 reader = csv.reader(f)
 for header in reader:
 break

# add row to CSV file
with open(myFile, "a", newline='') as f:
 writer = csv.DictWriter(f, fieldnames=header)
 writer.writerow(myDict)
</code></pre>

blocks|key|1100166|text|如果您使用pandas，则可以通过以下方式将数据帧附加到现有的CSV文件：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1100167|df.to_csv('log.csv',+mode='a',+index=False,+header=False)|code-block|syntax|javascript|1100168|使用mode='a‘，我们确保追加，而不是覆盖；使用header=False，我们确保只追加df行的值，而不是标题%2B值。|1100169|entityMap^0|0|0|0^^$0|@$1|2|3|4|5|6|7|K|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|L|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|M|8|@]|9|@]|A|$]]|$1|I|3|-4|5|6|7|N|8|@]|9|@]|A|$]]]|J|$]]

If you use pandas, you can append your dataframes to an existing CSV file this way:
<pre><code>df.to_csv('log.csv', mode='a', index=False, header=False)
</code></pre>
With mode='a' we ensure that we append, rather than overwrite, and with header=False we ensure that we append only the values of df rows, rather than header + values.

I am trying to add a new row to my old csv file. Basically, it gets updated each time I run the Python script. 

Right now I am storing the old csv rows values in a list and then deleting the csv file and creating it again with the new list value.

Wanted to know are there any better ways of doing this.

append new row to old csv file python

我正在尝试向旧的csv文件添加新行。基本上，它在我每次运行Python脚本时都会更新。现在，我将旧的csv行值存储在一个列表中，然后删除csv文件并使用新的列表值重新创建它。想知道有没有更好的方法。

问将新行追加到旧的csv文件python
EN

社区

活动

资源

关于

腾讯云开发者

热门产品

热门推荐

更多推荐

问将新行追加到旧的csv文件pythonEN

社区

活动

资源

关于

腾讯云开发者

热门产品

热门推荐

更多推荐

问将新行追加到旧的csv文件python
EN