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
Related
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.
I want to append some text to every line in my file
Here is my code
filepath = 'hole.txt'
with open(filepath) as fp:
line = fp.readline()
cnt = 1
while line:
#..........
#want to append text "#" in every line by reading line by line
text from .txt file
line = fp.readline()
cnt += 1
You can read the lines and put them in a list. Then you open the same file with write mode and write each line with the string you want to append.
filepath = "hole.txt"
with open(filepath) as fp:
lines = fp.read().splitlines()
with open(filepath, "w") as fp:
for line in lines:
print(line + "#", file=fp)
Assuming you can load the full text in memory, you could open the file, split by row and for each row append the '#'. Then save :-) :
with open(filepath, 'r') as f: # load file
lines = f.read().splitlines() # read lines
with open('new_file.txt', 'w') as f:
f.write('\n'.join([line + '#' for line in lines])) # write lines with '#' appended
I'll assume the file is small enough to keep two copies of it in memory:
filepath = 'hole.txt'
with open(filepath, 'r') as f:
original_lines = f.readlines()
new_lines = [line.strip() + "#\n" for line in original_lines]
with open(filepath, 'w') as f:
f.writelines(new_lines)
First, we open the file and read all lines into a list. Then, a new list is generated by strip()ing the line terminators from each line, adding some additional text and a new line terminator after it.
Then, the last line overwrites the file with the new, modified lines.
does this help?
inputFile = "path-to-input-file/a.txt"
outputFile = "path-to-output-file/b.txt"
stringToAPpend = "#"
with open(inputFile, 'r') as inFile, open(outputFile, 'w') as outFile:
for line in inFile:
outFile.write(stringToAPpend+line)
Hi I'm trying to finish this small piece of code for modifying csv files, I've got this far with some help:
edit... some more info.
Basically what I’m looking to do is make some small changes to the csv file depending on the project and parent issue in JIRA. Python will then make the changes to the csv file before it is then read into JIRA - that’s the second part of the program I’ve not even really looked at yet.
I’m only looking to change the BOX-123 type cells and leave the blank ones blank.
But the idea of the program is that I can use it to make some small changes to a template which will then automatically create some issues in JIRA.
import os
import csv
project = 'Dudgeon'
parent = 'BOX-111'
rows = (1,1007)
current = os.getcwd()
filename = 'test.csv'
filepath = os.path.join(os.getcwd(), filename)
#print(current)
#print(filename)
print(filepath)
with open(filepath, 'r') as csvfile:
readCSV = csv.reader(csvfile)
next(readCSV, None)
for row in readCSV:
print(row[16])
row_count =sum(1 for row in readCSV)
print(row_count)
with open(filepath, 'r') as infile, open('out.csv', 'w') as outfile:
outfile.write(infile.readline()) # write out the 1st line
for line in infile:
cols = line.strip().split(',')
cols[16] = project
outfile.write(','.join(cols) + '\n')
with open('out.csv', 'r') as infile, open('out1.csv', 'w') as outfile:
for row in infile:
if row % 2 != 0:
cols [15] = parent
outfile.write()
Any help really appreciated.
You want to use the row's index when comparing to 0. Use enumerate():
with open('out.csv', 'r') as infile, open('out1.csv', 'w') as outfile:
for rowidx,row in enumerate(infile):
cols = row.strip().split(',')
if rowidx % 2 != 0:
cols[15] = parent
outfile.write(cols)
You really should be using the csv module here, though. Untested but should get you started.
with open('out.csv', 'r') as infile, open('out1.csv', 'w') as outfile:
reader = csv.reader(infile)
writer = csv.writer(outfile)
for rowidx,row in enumerate(reader):
if rowidx % 2 != 0:
row[15] = parent
writer.write_row(row)
A friend helped me last night and this is what they came up with:
with open(filepath, 'r') as infile, open('out.csv', 'w') as outfile:
outfile.write(infile.readline()) # write out the 1st line
for line in infile:
cols = line.strip().split(',')
cols[16] = project
outfile.write(','.join(cols) + '\n')
with open('out.csv', 'r') as infile, open('out1.csv', 'w') as outfile:
outfile.write(infile.readline()) # write out the 1st line
lineCounter = 0
for line in infile:
lineCounter += 1
cols = line.strip().split(',')
if lineCounter % 2 != 0:
cols[15] = parent
outfile.write(','.join(cols) + '\n')
At the moment I've got this function:
def writer(file_name)
open_file = open(file_name,"r+", newline='')
csv_output = csv.writer(open_file)
csv_output.writerow(student)
open_file.close()
where student is:
"string_1","string_2",int
I'm looking to read through the file first and check if the "string_1" that I'm writing matches any of the "string_1"s already written, but I can't find a built-in function that lets me read each line and store it as a list.
First, you have to open the file for reading, go through the file line by line and return, if "string_1" is found:
def append_student(file_name, student)
with open(file_name, "r") as f:
for line in csv.reader(f):
if line[0] == student[0]:
return
with open(file_name, "a") as f:
csv.writer(f).writerow(student)
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: