Numpy Array 没有将数组的所有值复制到 csv 文件

Question

我在将数组保存到 csv 文件时遇到格式化问题，每次我运行程序都得到不同的结果，有时不显示字符串“creditCard”在传播 sheet 但所有其他细节都是。有时是这样。我的代码中是否有明显的原因导致这种不稳定？我已附上相关代码

def start():


dtype = [('Name', (np.str_, 10 )), ('Number of uses', np.int32), ('Card Value', np.float64)]
defaultCardArray = np.array([("creditCard",4,200)],dtype=dtype)
np.savetxt('creditCards.csv', defaultCardArray, delimiter=',', fmt=['%s' , '%d', '%f'],
           header='Name,Number of Uses, Card Value', comments='')e here

创建文件后，我还有以下代码可以在之后添加每张卡片。默认卡在文件创建时加载正常，但以下卡阵列是我遇到的问题有代码要求用户输入并保存到变量而不会出错，所以我没有在此处包含它

cardArray = np.array([creditCard,itemLimit,cardValueInput]).reshape(1,3)
file = open(r'creditCards.csv', 'at', newline ='') 
with file:     
    write = csv.writer(file) 
    write.writerows(cardArray) 
    file.close()

image of the output I am getting in the csv

Answer 1

对于您的代码，我认为当您创建新的 cardArray 时，您没有像为初始数组那样指定类型，这可能是个问题。

无论如何，numpy 可能不是这里使用的最佳库。
对于这种数据，我会使用 pandas:

import pandas as pd

header = ['Name', 'Number of Uses', 'Card Value']

def start():
# create default dataset
  default_card_df =  pd.DataFrame(["creditCard",4,200], columns=header)
  default_card_df.to_csv('creditCards.csv', sep=",")

def add_card(name, itemLimit, cardValueInput):
# read csv, add new data, save to csv
  df = pd.read_csv('creaditCards.csv', sep=",")
  new_df = pd.DataFrame([name, itemLimit, cardValueInput], columns=header)
  updated_df = pd.concat(df, new_df)
  updated_df.to_csv('creditCards.csv', sep=",")

Answer 2

您的初始写作：

In [281]: np.savetxt('creditCards.csv', defaultCardArray, delimiter=',', fmt=['%
     ...: s' , '%d', '%f'],
     ...:            header='Name,Number of Uses, Card Value', comments='')

产生：

In [282]: cat creditCards.csv
Name,Number of Uses, Card Value
creditCard,4,200.000000

如果以追加模式打开，我们可以向该文件添加更多条目：

In [284]: with open('creditCards.csv','a') as f:
     ...:     np.savetxt(f, defaultCardArray, delimiter=',', fmt=['%s' , '%d', '
     ...: %f'])
     ...: 
In [285]: cat creditCards.csv
Name,Number of Uses, Card Value
creditCard,4,200.000000
creditCard,4,200.000000

要继续使用具有相同 fmt 的 savetxt，您应该使用原始 dtype.

创建数组

.

In [286]: newcards = np.zeros(3,dtype=dtype)
In [287]: newcards
Out[287]: 
array([('', 0, 0.), ('', 0, 0.), ('', 0, 0.)],
      dtype=[('Name', '<U10'), ('Number of uses', '<i4'), ('Card Value', '<f8')])

In [289]: newcards['Name']='foobar'
In [290]: newcards['Card Value']=np.arange(10,40,10)
In [291]: newcards
Out[291]: 
array([('foobar', 0, 10.), ('foobar', 0, 20.), ('foobar', 0, 30.)],
      dtype=[('Name', '<U10'), ('Number of uses', '<i4'), ('Card Value', '<f8')])

In [292]: with open('creditCards.csv','a') as f:
     ...:     np.savetxt(f, newcards, delimiter=',', fmt=['%s' , '%d', '%f'])
     ...: 

In [293]: cat creditCards.csv
Name,Number of Uses, Card Value
creditCard,4,200.000000
creditCard,4,200.000000
foobar,0,10.000000
foobar,0,20.000000
foobar,0,30.000000

Numpy Array 没有将数组的所有值复制到 csv 文件

Numpy Array is not copying over all values of the array to csv file

python

numpy

spyder