[英]Pandas is not Reading Entire .CSV File
I have been testing some issues I've had with Pandas.我一直在测试我在 Pandas 上遇到的一些问题。 My end goal here is to add data to a .csv.
我的最终目标是将数据添加到 .csv。 While figuring out ways to change a .csv, I settled on this method:
在寻找更改 .csv 的方法时,我选择了这种方法:
import pandas
data = pandas.read_csv('path/to/my/script/test.csv')
data.iat[1,1] = 'DataHere'
data.to_csv('path/to/my/script/test.csv', index=False, header=False)
This code worked somewhat correctly.这段代码工作得有些正确。
DataHere
goes to the second row and second column, which is correct (because [0,0] is the first row and column. Note: it's not the normal x,y coordinates, it's more like y,x). DataHere
转到第二行第二列,这是正确的(因为 [0,0] 是第一行和第一列。注意:它不是正常的 x,y 坐标,它更像是 y,x)。
test.csv before code (6x6):代码前的 test.csv (6x6):
yes,yes,yes,yes,yes,yes
yes,yes,yes,yes,yes,yes
yes,yes,yes,yes,yes,yes
yes,yes,yes,yes,yes,yes
yes,yes,yes,yes,yes,yes
yes,yes,yes,yes,yes,yes
test.csv after code (6x5):代码后的test.csv(6x5):
yes,yes,yes,yes,yes,yes
yes,DataHere,yes,yes,yes,yes
yes,yes,yes,yes,yes,yes
yes,yes,yes,yes,yes,yes
yes,yes,yes,yes,yes,yes
It gets rid of the lowermost row for some reason!由于某种原因,它摆脱了最下面的一行! So I did some messing with the parameters of
pandas.read_csv('path/to/my/script/test.csv')
to fix this problem, and got this:所以我对
pandas.read_csv('path/to/my/script/test.csv')
的参数做了一些处理来解决这个问题,得到了这个:
data = pandas.read_csv('path/to/my/script/test.csv', nrows=6, skip_blank_lines=False)
I added nrows=6
to make it read 6 rows, although I do intend to make it higher in the future.我添加了
nrows=6
以使其读取6行,尽管我确实打算在将来使它更高。 I added skip_blank_lines=False
because I want to be able to add data to blank cells.我添加了
skip_blank_lines=False
因为我希望能够将数据添加到空白单元格。
When I ran this new code (after changing the csv to its previous 6x6 state), it didn't help.当我运行这个新代码时(将 csv 更改为之前的 6x6 状态后),它没有帮助。 It still erases the 6th row.
它仍然会擦除第 6 行。
import pandas
data = pandas.read_csv('path/to/my/script/test.csv', nrows=6, skip_blank_lines=False)
data.iat[1,1] = 'DataHere'
data.to_csv('path/to/my/script/test.csv', index=False, header=False)
I also tried data.iat[6,3] = 'DataHere'
instead of data.iat[1,1] = 'DataHere'
, which returned this error:我还尝试
data.iat[6,3] = 'DataHere'
而不是data.iat[1,1] = 'DataHere'
,它返回了这个错误:
IndexError: index 6 is out of bounds for axis 0 with size 5
This shows that not only it is erasing the last row, but that it cannot add data to a blank cell.这表明它不仅在擦除最后一行,而且无法将数据添加到空白单元格。 To make sure that it was the fault of this line:
data = pandas.read_csv('path/to/my/script/test.csv', nrows=6, skip_blank_lines=False)
, I put print(data)
in the line immediately after it and got this output (plus the previously stated errors).为了确保这是这一行的错:
data = pandas.read_csv('path/to/my/script/test.csv', nrows=6, skip_blank_lines=False)
,我把print(data)
放在了这一行紧随其后并得到这个输出(加上前面提到的错误)。 There should be a 5th row of 'yes' there.那里应该有第 5 行“是”。 So my two problems are:
所以我的两个问题是:
pandas.read_csv('path/to/my/script/test.csv')
uses the first row as a header row. pandas.read_csv('path/to/my/script/test.csv')
使用第一行作为标题行。 Your test.csv
does not have a header row.您的
test.csv
没有标题行。 So it is likely that the first row (data row) in test.csv
is being read as a header row.因此很可能
test.csv
中的第一行(数据行)被读取为标题行。 Giving you 5 data rows and not 6 as you expect.给你 5 个数据行,而不是你期望的 6 个。
This could be happening这可能正在发生
sim_csv = io.StringIO(
'''yes,yes,yes,yes,yes,yes
yes,yes,yes,yes,yes,yes
yes,yes,yes,yes,yes,yes
yes,yes,yes,yes,yes,yes
yes,yes,yes,yes,yes,yes
yes,yes,yes,yes,yes,yes'''
)
data = pd.read_csv(sim_csv)
print(data)
yes yes.1 yes.2 yes.3 yes.4 yes.5
0 yes yes yes yes yes yes
1 yes yes yes yes yes yes
2 yes yes yes yes yes yes
3 yes yes yes yes yes yes
4 yes yes yes yes yes yes
Then when you write out the CSV with to_csv(header=None)
you lose that first row of data.然后,当您使用
to_csv(header=None)
写出 CSV 时,您会丢失第一行数据。
To get around this you could do:为了解决这个问题,你可以这样做:
pandas.read_csv('path/to/my/script/test.csv', header=None)
or you could do this:或者你可以这样做:
pandas.to_csv('path/to/my/script/test.csv')
Just make sure that you're consistent with header=None
, you either set both pandas.read_csv
and pandas.to_csv
to header=None
, or just remove it, don't have header=None
on one or the other.只要确保您与
header=None
一致,您可以将pandas.read_csv
和pandas.to_csv
都设置为header=None
,或者只是删除它,不要在其中一个或另一个上设置header=None
。
Adding a row (cell to a new row)添加行(单元格到新行)
You can add a row (cell to a row) by using the index.您可以使用索引添加一行(单元格到一行)。 For example if you had:
例如,如果您有:
yes yes.1 yes.2 yes.3 yes.4 yes.5
0 yes yes yes yes yes yes
1 yes yes yes yes yes yes
2 yes yes yes yes yes yes
3 yes yes yes yes yes yes
4 yes yes yes yes yes yes
Then you could do: (note that this is .at
and not .iat
)然后你可以这样做:(注意这是
.at
而不是.iat
)
df.at[5,'yes'] = 'yes'
Which will give you:这会给你:
yes yes.1 yes.2 yes.3 yes.4 yes.5
0 yes yes yes yes yes yes
1 yes yes yes yes yes yes
2 yes yes yes yes yes yes
3 yes yes yes yes yes yes
4 yes yes yes yes yes yes
5 yes NaN NaN NaN NaN NaN
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