everytime i run my code it overwrites to first line of output.txt.
How can i make it so it writes to a new line every time?
def calculate_averages(input_file_name, output_file_name):
with open(input_file_name) as f:
reader = csv.reader(f)
for row in reader:
name = row[0]
these_grades = list()
for grade in row[1:]:
these_grades.append(int(grade))
with open(output_file_name, 'w') as external_file:
print(name, mean(these_grades), end='\n', file=external_file)
external_file.close()
This is happening because you are reopening your file in "w" mode for each row, which will overwrite your file. You can open the file outside of the for loop to avoid this behaviour:
import numpy as np
import csv
def calculate_averages(input_file_name, output_file_name):
with open(input_file_name) as f:
reader = csv.reader(f)
with open(output_file_name, 'w') as external_file:
for row in reader:
name = row[0]
mean_of_grades = np.mean([int(x) for x in row[1:]])
external_file.write(f"{name} {mean_of_grades}\n")
You can use a different mode for this:
Instead of with open(output_file_name, "w") as external_file:,
Use with open(output_file_name, "a") as external_file.
"a" stands for append, which will append the text to the end of the file.
I hope I understood your question right.
Related
I want to create a program which generates numbers from 0 to 100000 and stores it in a file then, remove the numbers i give as input
I have done the code for generating the numbers and storing them in a csv file
import csv
nums = list(range(0,100000))
with open('codes.csv', 'w') as f:
writer = csv.writer(f)
for val in nums:
writer.writerow([val])
and i tried to delete the row i wanted with this
import csv
import os
lines = list()
while True:
members= input("Please enter a number to be deleted: ")
with open('codes.csv', 'r') as readFile:
reader = csv.reader(readFile)
for row in reader:
lines.append(row)
for field in row:
if field == members:
lines.remove(row)
os.remove('codes.csv')
with open('codes.csv', 'a+') as writeFile:
writer = csv.writer(writeFile)
writer.writerows(lines)
but the file size is multiplying each time i remove a number, please help
Add check before appending to your list, something like this should work:
with open('codes.csv', 'r') as readFile:
reader = csv.reader(readFile)
for row in reader:
if all(field != members for field in row):
lines.append(row)
Ps: don't forget to clear lines by adding lines = [] at the beginning of the while loop (I assume you know what you're doing).
There a two problems:
The lines list is never cleared. Whenever a number is entered, everything is written again to lines.
When writing, the file is opened with the a+ attributes, which means "append and update" file.
Try to recreate the list within the outer while loop and override the file contents by opening the file with attribute w, like this:
import csv
import os
while True:
members= input("Please enter a number to be deleted: ")
lines = list()
with open('codes.csv', 'r') as readFile:
reader = csv.reader(readFile)
for row in reader:
lines.append(row)
for field in row:
if field == members:
lines.remove(row)
os.remove('codes.csv')
with open('codes.csv', 'w') as writeFile:
writer = csv.writer(writeFile)
writer.writerows(lines)
I'm trying to make a program which stores a list of names in a CSV file, and I'm trying to add a function to delete rows, which isn't working as it deletes everything in the CSV file.
I've tried using writer.writerow(row), which hasn't worked.
memberName = input("Please enter a member's name to be deleted.")
imp = open('mycsv.csv' , 'rb')
out = open('mycsv.csv' , 'wb')
writer = csv.writer(out)
for row in csv.reader(imp):
if row == memberName:
writer.writerow(row)
imp.close()
out.close()
I expected the program to only delete rows which contained memberName, but it deletes every row in the CSV file.
How do I change it to only delete a single row?
You can't write to the same file while reading it. Instead, use another file for output, e.g.:
import csv
member_name = input("Please enter a member's name to be deleted: ")
with open('in_file.csv') as in_file, open('out_file.csv', 'w') as out_file:
reader = csv.reader(in_file)
writer = csv.writer(out_file)
for row in reader:
if member_name not in row: # exclude a specific row
writer.writerow(row)
Alternatively, you could store needed rows in memory and write them back to the input file after resetting the file pointer:
import csv
member_name = input("Please enter a member's name to be deleted: ")
with open('in_file.csv', 'r+') as in_file:
reader = csv.reader(in_file)
rows = [row for row in csv.reader(in_file) if member_name not in row]
in_file.seek(0)
in_file.truncate()
writer = csv.writer(in_file)
writer.writerows(rows)
This worked for me: you could write the contents of the csv file to a list, then edit the list in python, then write the list back to the csv file.
lines = list()
memberName = input("Please enter a member's name to be deleted.")
with open('mycsv.csv', 'r') as readFile:
reader = csv.reader(readFile)
for row in reader:
lines.append(row)
for field in row:
if field == memberName:
lines.remove(row)
with open('mycsv.csv', 'w') as writeFile:
writer = csv.writer(writeFile)
writer.writerows(lines)
I'm trying to edit a single row in a csv file. I've got a CSV file that looks like the bellow:
TYPE|FOOD TYPE|FEED TIME|WASH TIME
LION|MEAT|4H|1D
FOX|MEAT|5H|3D
HEN|SEED|6H|6D
FISH|PLANTS|7H|99D
I want to edit the row based on its TYPE. If the user wants to edit the FOX row they only need to type FOX when prompted. The issue I'm facing is that the I can't edit the file for some reason.
My code is bellow, I open the existing db, find the row in question, change it, then write it, along with the other rows, into a temp file that I can overwrite the original with.
def edit_animal_entry(type):
with open(animal_csv, 'r') as file_read:
reader = csv.reader(file_read, delimiter="|")
with open(temp, 'w') as file_write:
writer = csv.writer(file_write)
for row in reader:
print(f"{' | '.join(row)}")
if row[0] == type:
animal_type, animal_food, animal_feed, animal_wash = animal_inputs()
writer.writerow([animal_type, animal_food, (animal_feed+"H"), (animal_wash+"D")])
else:
writer.writerow(row)
shutil.move(temp, animal_csv)
You've 'closed' the read file by stopping the with block before reading anything out of it. Therefore you aren't looping over your input file. A solution would be to open the input and the output file in the same with statement:
def edit_animal_entry(type):
with open(animal_csv, 'r') as file_read, open(temp, 'w') as file_write:
reader = csv.reader(file_read, delimiter="|")
writer = csv.writer(file_write)
for row in reader:
print(f"{' | '.join(row)}")
if row[0] == type:
animal_type, animal_food, animal_feed, animal_wash = animal_inputs()
writer.writerow([animal_type, animal_food, (animal_feed+"H"), (animal_wash+"D")])
else:
writer.writerow(row)
shutil.move(temp, animal_csv)
I have a txt file and I want to save each line as a list in a new file with fname as the new file name. But the output is not being saved. What am I missing?
import csv
with open('file.txt', 'rU') as csvfile:
reader = csv.reader(csvfile, delimiter='\t')
i = 1
for line in reader:
fname = line[0] + line[1]
#print fname
with open(fname, 'w') as out:
out.write(line)
i +=1
To do what you want, you need to fix two things, one is to open the output files in "append" mode so their previous contents aren't wiped-out everytime something additional is written to them.
Secondly you need some way to know the raw data from the file for each csv row it reads. This can be difficult when you use an extension like the csv module and don't know the internals (which you shouldn't use anyway).
To work around that in this case, you can pass a custom csvfile argument to the csv.reader that will give you the information needed. Basically a small preprocessor of the data being read. Here's what I mean:
import csv
def pre_reader(file):
"""Generator that remembers last line read."""
for line in file:
pre_reader.lastline = line
yield line
with open('test_gen.csv', 'rU') as csvfile:
reader = csv.reader(pre_reader(csvfile), delimiter='\t')
i = 1
for line in reader:
fname = line[0] + line[1]
#print fname
with open(fname, 'a') as out:
out.write(pre_reader.lastline)
i +=1
Change:
with open(fname, 'w') as out:
out.write(line)
To:
with open(fname, 'a') as out:
out.write(line)
w Opens a file for writing only. Overwrites the file if the file exists. If the file does not exist, creates a new file for writing.
a Opens a file for appending. The file pointer is at the end of the file if the file exists. That is, the file is in the append mode. If the file does not exist, it creates a new file for writing.
Better way:
import csv
with open('file.txt', 'rU') as csvfile, open(fname, 'w') as out:
reader = csv.reader(csvfile, delimiter='\t')
i = 1
for line in reader:
fname = line[0] + line[1]
out.write(line)
You cannot write a list so change penultimate line to **out.write(str(line))**
import csv
with open('file.txt', 'rU') as csvfile:
reader = csv.reader(csvfile, delimiter='\t')
i = 1
for line in reader:
fname = line[0] + line[1]
#print fname
with open(fname, 'w') as out:
------> out.write(str(line))
i +=1
I have data in a file and I need to write it to CSV file in specific column. The data in file is like this:
002100
002077
002147
My code is this:
import csv
f = open ("file.txt","r")
with open("watout.csv", "w") as output:
for line in f :
c.writerows(line)
It is always writes on the first column. How could I resolve this?
Thanks.
This is how I solved the problem
f1 = open ("inFile","r") # open input file for reading
with open('out.csv', 'w',newline="") as f:up # output csv file
writer = csv.writer(f)
with open('in.csv','r') as csvfile: # input csv file
reader = csv.reader(csvfile, delimiter=',')
for row in reader:
row[7] = f1.readline() # edit the 8th column
writer.writerow(row)
f1.close()
python 2 users replace
with open('out.csv', 'w',newline="") as f:
by
with open('out.csv', 'wb') as f: