Python, adding header to new .csv file-CodePudding

Greetings and thanks in advance for reading my question.

I'm creating a temperature logger program that records date, time, and temperatures. The program should create a new .csv file that includes data and column headers. However I'm finding it difficult to add headers to the new file. I tried using two while loops, one before the other and the file didn't seem to append the headers, but recorded the data ok. Then I tried to nest in an if statement and it wrote the headers but also added them to the end of every new line of data (see picture below).

Please share any thoughts.

My code is as follows:

datetime1 = str(datetime.now())

#create new file with datestamp
extension = ".csv"
file_name = datetime1   extension
file1 = open(file_name, 'a')

#add header to .csv
header = str("Date,Time,Minutes,InletTemp,ControlTemp,BedTemp,OutletTemp")

#x = 1
#while x >= 1:
#    file1 = open(file_name, 'a')
#    file1.write(header)
#    x -= 1

#start button function
def start():
    while(1):
        x = 1
        if x >= 1:
            file1 = open(file_name, 'a')
            file1.write(header)
      
            
#gather the data from each thermocouple
        t1 = THERMO.getTEMP(0,1)
        t2 = THERMO.getTEMP(0,2)
        t3 = THERMO.getTEMP(0,3)
        t4 = THERMO.getTEMP(0,4)

#themoplate LED cycle
        THERMO.toggleLED(0)
        
#write sensor data to a file
        datetime2 = datetime.now()
        data = str(datetime2)   ','   ' '   str(t1)   ','   str(t2)   ','   str(t3)   ','   str(t4)
        file1 = open(file_name, 'a') 
        file1.write('\n')
        file1.write(data)
        
#write sensor data to the console
        print (str(datetime2))
        print ('Temperature on Channel 1:',t1)
        print ('Temperature on Channel 2:',t2)
        print ('Temperature on Channel 3:',t3)
        print ('Temperature on Channel 4:',t4)
        time.sleep(1)

CodePudding user response：

Something like this is closer to what you want. This leaves the file open continuously. If you don't like that, do file1.close() after printing the header, and file1=open(file_name, 'a') before writing the data and file1.close() after.

datetime1 = str(datetime.now())

#create new file with datestamp
extension = ".csv"
file_name = datetime1   extension

#add header to .csv
header = "Date,Time,Minutes,InletTemp,ControlTemp,BedTemp,OutletTemp"

#start button function
def start():
    file1 = open(file_name, 'w')
    print(header, file=file1)

    while(1):     
            
#gather the data from each thermocouple
        t1 = THERMO.getTEMP(0,1)
        t2 = THERMO.getTEMP(0,2)
        t3 = THERMO.getTEMP(0,3)
        t4 = THERMO.getTEMP(0,4)

#themoplate LED cycle
        THERMO.toggleLED(0)
        
#write sensor data to a file
        datetime2 = datetime.now()
        data = ','.join( (str(datetime2), str(t1), str(t2), str(t3), str(t4) )
        print( data, file=file1)
        
#write sensor data to the console
        print (str(datetime2))
        print ('Temperature on Channel 1:',t1)
        print ('Temperature on Channel 2:',t2)
        print ('Temperature on Channel 3:',t3)
        print ('Temperature on Channel 4:',t4)
        time.sleep(1)

CodePudding user response：

import csv # at the top of your program

Then use a DictWriter to build the CSV. That will put in the headers for you.

CodePudding user response：

It looks to me like you're re-opening and re-headering your file after every line, meaning the header gets concatenated to the end of every line. To fix this, fix your while-loop, like so:

def start():
    x = 1
    while 1:
        if x == 1:
            file1 = open(file_name, 'w')
            file1.write(header)
            file1.close()
    # ...etc

That way, you only write the header exactly once when the loop starts, and not every time a reading is recorded. I also recommend calling close() every time you finish writing to the file.

CodePudding user response：

You set x=1 at the beginning of the while(True) loop and it is never updated, that's why it gets added every line.

I think you should, first open the file in write mode, something like:

with open(file_name, 'w') as file1:
    file1.write(header)

which will erase previous data and write your header. And then you open the file once before the while(True) in append mode as you were doing (file1 = open(file_name, 'a')).

CodePudding user response：

A cleaner solution is to use the csv module to write the data. Open the file once at the beginning to write the header, and then append new data as collected:

from datetime import datetime
import csv
import time


now = datetime.now()
filename = f'sensors_{now:%Y%m%d%H%M%S}.csv'

# Write mode to start a new file
with open(filename, 'w', newline='') as f:
    writer = csv.writer(f)
    writer.writerow('Date Time Minutes InletTemp ControlTemp BedTemp OutletTemp'.split())

def start():
    while True:
        # Simulate data
        t1,t2,t3,t4 = 45.1,45.2,45.3,45.4

        # collect column data in a list
        now = datetime.now()
        row = [now.strftime('%Y-%m-%d'),now.strftime('%H:%M:%S.%f'),'',t1,t2,t3,t4]

        # append new data
        with open(filename, 'a', newline='') as f:
            writer = csv.writer(f)
            writer.writerow(row)

        # Write sensor data to the console
        print(now)
        print('Temperature on Channel 1:',t1)
        print('Temperature on Channel 2:',t2)
        print('Temperature on Channel 3:',t3)
        print('Temperature on Channel 4:',t4)
        time.sleep(1)

start()

Example output:

sensors_20211028094726.csv:

Date,Time,Minutes,InletTemp,ControlTemp,BedTemp,OutletTemp
2021-10-28,09:47:26.710602,,45.1,45.2,45.3,45.4
2021-10-28,09:47:27.718613,,45.1,45.2,45.3,45.4
2021-10-28,09:47:28.734657,,45.1,45.2,45.3,45.4
2021-10-28,09:47:29.750682,,45.1,45.2,45.3,45.4