Question

我正在尝试操纵pandas数据帧以从随机整数生成器的输出中选择随机索引，然后使用该值，并将“Used”列设置为yes，再次保存csv。

我的代码如下：

import random
import pandas

# Read in the dataframe:
df = pandas.read_csv('./data/voucher_codes.csv', encoding='utf-8')

# Generate a random integer (this would be nice if the max value was the number of rows - but I'll figure this out later!)
index = random.randint(0, 3)

# Store this code in memory selecting only when Used = 'No':
voucher_code = df.loc[df['Used'] == 'No'].iloc[[index]]['Voucher Code'].values[0]

# Update the column associated to the above voucher code to "Yes'
df.loc[df['Voucher Code'] == voucher_code]['Used'] = 'Yes'

# Save said dataframe, to be consistent with what voucher codes have been used:
df.to_csv('./data/voucher_codes.csv', sep=',')

.csv不会被覆盖！

示例数据可能很有用：

000001,No
000002,No
000003,No
000004,No

这是来自@ ALollz建议的数据框：

,Unnamed: 0,Voucher Code,Used
0,0,000001,No
1,1,000002,No
2,2,000003,No
3,3,000004,No

Answer 1

我运行了您的代码并收到此错误，因此DataFrame未被修改：

A value is trying to be set on a copy of a slice from a DataFrame.
Try using .loc[row_indexer,col_indexer] = value instead

See the caveats in the documentation: http://pandas.pydata.org/pandas-docs/stable/indexing.html#indexing-view-versus-copy

为了匹配.loc [row_indexer，col_indexer]的格式，我更改了行

df.loc[df['Voucher Code'] == voucher_code, 'Used'] = 'Yes'

P.S。您可以使用df.shape

生成最多行数的随机整数

index = random.randint(0, df.shape[0])

希望这有帮助

操作pandas数据帧然后保存更改

1 个答案: