How to write CSV files with Python using print statements with variables in them

Question

I'm a noob here and I have pretty straight forward question with writing CSV output files with Python. I've been googling this for a while and I can't find an answer to my q. I have a bunch of tasks which have to output answers to the terminal as well as write the answers to a CSV output file. I've got all the correct answers in the terminal but I can't figure out how to write them to a CSV file. My print statements contain variables, and I need the value of the variable printed. IE "The total profit/loss for this period is: $22564198" should be printed to the CSV not the print statement format which is: 'The total profit/loss for this period is: ${total}'

I'm copying my code below.

import os 
import csv

date = []
profloss = []
changes = []
total = 0
totalChange = 0 
mo2mo = {}


budget_csv = os.path.join(xxxxxx)

with open(budget_csv) as csvfile:
    csvreader = csv.reader(csvfile, delimiter=",")

#splitting the two columns into seperate lists
    for row in csvreader:
        date.append(row[0])
        profloss.append(row[1])
    
#removing header rows
    date.pop(0)
    profloss.pop(0)

#printing how many months are in the data set
    dataLen = len(date)
    countMonths = "This data set has " + str(len(date)) + " months." 
    
#calculating total profit/loss
    for i in range(0, len(profloss)):
        profloss[i] = int(profloss[i])
        total = total + (profloss[i])
    print(f'The total profit/loss for this period is: ${total}')

#calculating the difference between months and adding it to a list
    for i in range(0, len(profloss)-1):
        difference = (profloss[i+1]) - (profloss[i])
        changes.append(difference)

#removing the first element in date to make a dictionary for dates: changes
    date.pop(0)
    
#creating a dictionary of months as keys and change as values, starting with the second month
    mo2mo = {date[i]: changes[i] for i in range(len(date))}
   
#calculating the average change from one month to the next
    
    for i in range(0, len(changes)):
        totalChange = totalChange + changes[i] 
    avChange = totalChange/len(changes)
    print(f'The average change from month to month for this dataset is: {round((avChange),2)}')

#getting the month with the maximum increase
    keyMax = max(mo2mo, key= lambda x: mo2mo[x])

    for key,value in mo2mo.items():
        if key == keyMax:
            print(f'The month with the greatest increase was: {key} ${value}')
    

#getting the month with the maximum decrease
    keyMin = min(mo2mo, key= lambda x: mo2mo[x])
    for key, value in mo2mo.items():
        if key == keyMin:
            print(f'The maximum decrease in profits was: {key} ${value}')
    

outputCSV = ("countMonths",)
output_path = os.path.join("..", "output", "PyBankAnswers.csv")
#writing outcomes to csv file
with open(output_file,"w") as datafile:
    writer = csv.writer(datafile)
    for row in writer.writerow()

I've only got experience printing whole lists to csv files and not actual statements of text. I've tried to find how to do this but I'm not having luck. There's got to be a way without me just writing out the sentence I want printed by hand and having the CSV writer print that statement? OR do I just have to copy the sentence from the terminal and then print those statements row by row?

Answer 1

The print() function accepts a file option to specify that the output should be written to an open file stream. So you can make all your print() statements twice, once to the terminal and then to the file. To avoid all this duplication, you can put that into a function. Then call that instead of print() everywhere.

import os 
import csv

date = []
profloss = []
changes = []
total = 0
totalChange = 0 
mo2mo = {}

def print_to_terminal_and_file(f, *args, **kwargs):
    print(*args, **kwargs)
    print(*args, file=f, **kwargs)

budget_csv = os.path.join(xxxxxx)

with open(budget_csv) as csvfile:
    csvreader = csv.reader(csvfile, delimiter=",")

    #splitting the two columns into seperate lists
    for row in csvreader:
        date.append(row[0])
        profloss.append(int(row[1]))
    
#removing header rows
date.pop(0)
profloss.pop(0)

output_path = os.path.join("..", "output", "PyBankAnswers.txt")
#writing outcomes to text file
with open(output_file,"w") as datafile:

    #printing how many months are in the data set
    print_to_terminal_and_file(datafile, f"This data set has {len(date)} months.")

    #calculating total profit/loss
    total = sum(profloss)
    print_to_terminal_and_file(datafile, f'The total profit/loss for this period is: ${total}')

    #calculating the difference between months and adding it to a list
    for i in range(0, len(profloss)-1):
        difference = (profloss[i+1]) - (profloss[i])
        changes.append(difference)

    #removing the first element in date to make a dictionary for dates: changes
    date.pop(0)

    #creating a dictionary of months as keys and change as values, starting with the second month
    mo2mo = {date[i]: changes[i] for i in range(len(date))}

    #calculating the average change from one month to the next

    for i in range(0, len(changes)):
        totalChange = totalChange + changes[i] 
    avChange = totalChange/len(changes)
    print_to_terminal_and_file(datafile, f'The average change from month to month for this dataset is: {round((avChange),2)}')

    #getting the month with the maximum increase
    keyMax = max(mo2mo, key= lambda x: mo2mo[x])

    for key,value in mo2mo.items():
        if key == keyMax:
            print_to_terminal_and_file(datafile, f'The month with the greatest increase was: {key} ${value}')


    #getting the month with the maximum decrease
    keyMin = min(mo2mo, key= lambda x: mo2mo[x])
    for key, value in mo2mo.items():
        if key == keyMin:
            print_to_terminal_and_file(datafile, f'The maximum decrease in profits was: {key} ${value}')