python - 在使用 python 将值写入 csv 文件之前将值与字段名进行比较

Question

我使用此代码将值与其附属字段名称进行比较，然后将其存储在 csv 文件中以检查正确的列，因为每次重新启动计算机时，字典中传感器的顺序都会自动更改。这就是为什么我必须先控制 dict 中值的位置，然后再将其存储在 csv 文件中，否则我会得到一个困惑的 csv 文件，如下例所示，其中提供的值温度为 1000 [°C]，光度为 10 [lux]

import csv
from datetime import datetime
import os
import time
from collections import OrderedDict
from time import sleep


Datum = time.strftime("%Y-%m-%d")
Time = datetime.now().replace(microsecond=0).isoformat()

data = {'Stecker Energy': '2.37', 'Stromzaehler Strom L1 [A]': '0.0', '1OG Ultraviolet': '0.0','Stecker EG  Energie [kWh]': '4.3'}

filename = Datum + 'SOF.csv'
if not os.path.isfile(filename):
    outfile = open(filename, "w")
    lineKey = ""
    for x in data.keys():
        lineKey+= x + ","
    lineKey = 'Time '+ "," + lineKey[:-1]+"\n" # Delete last character and add new line
    outfile = open(filename, "a")
    outfile.write(lineKey)
    outfile.close()

#check first line of  fieldnames 
with open(filename,'r') as myFile:
    reader = csv.DictReader(myFile)
    fieldnames = reader.fieldnames
    myFile.close()
#Compare the values with their  keys (fieldnames)
with open(filename,'a') as outfile:
    lineValue = ""
    for sensor, value  in data.items():
        if sensor in data.items()==sensor in fieldnames:
            v = data[sensor]
            print("v", v)
            lineValue+= str(v) + "," 
    lineValue = Time + "," + lineValue[:-1] + "\n"
    print(lineValue)
    outfile.write(lineValue)
    outfile.close()

问题是当我检查 CSV 文件时，我发现值写在错误的列中，这意味着Examlpe 的字段名称错误:

CSV 文件中此问题的示例

CSV 文本示例

时间，Stromzaehler Strom L1 [A]，Stecker Energy，1OG 紫外线，Stecker EG Energie [kWh]2017-11-21T17:56:10,2.37,0.0,0.0,4.32017-11-21T17:56:26,4.3,0.0,0.0,2.372017-11-21T17:56:28,0,0.0,2.37,4.32017-11-21T17:56:30,0,2.37,0.0,4.3

data = {'Stecker Energy': '', 'Stromzaehler Strom L1 [A]': '', '1OG Ultraviolet': '','Stecker EG  Energie [kWh]': ''}

Answer 1

for sensor, value  in data.items():
    if sensor in data.items()==sensor in fieldnames:
        v = data[sensor]
        print("v", v)
        lineValue+= str(v) + "," 

这对我来说看起来不对。如果您只想迭代所有字段名称(“时间”除外)并添加 data 中的值对应于这些字段，同时还为 data 中不存在的值设置“n/a” ，那么我建议这样做:

with open(filename,'a') as outfile:
    lineValue = ""
    for fieldname in fieldnames[1:]: #skip the first one, since that's Time, which we have a custom value for already.
        v = data.get(fieldname, "n/a")
        lineValue += str(v) + ","
    lineValue = Time + "," + lineValue[:-1] + "\n"
    print(lineValue)
    outfile.write(lineValue)
    outfile.close()

<小时/>

额外建议:手动在值之间添加逗号是一种容易出错的方法。如果可能，请使用DictWriter ，它可以为您解决大多数格式问题。

with open(filename,'a') as outfile:
    writer = csv.DictWriter(outfile, fieldnames)
    row = {}    
    for fieldname in fieldnames: #no need to skip Time here, we'll just overwrite it later.
        row[fieldname] = data.get(fieldname, "n/a")
    row["Time "] = Time
    writer.writerow(row)

如果您坚持不这样做，至少将值存储在列表中，您join最后一次:

with open(filename,'a') as outfile:
    values = [Time]
    for fieldname in fieldnames[1:]:
        v = data.get(fieldname, "n/a")
        values.append(str(v))
    outfile.write(",".join(values) + "\n")

<小时/>

额外奖励建议:如果这些解决方案在您不想要的行之间添加额外的空行，则可以使用 newline="" 打开文件参数(如果使用 Python 3):

with open(filename,'a', newline="") as outfile:

...或者以二进制模式打开文件(如果使用 Python 2):

with open(filename,'ab') as outfile: