So, I'm trying to make a function to delete a row from my csv depending on the Name given by the parameter.
Original File:
Janet,5,cats
Wilson,67,dogs
Karen,8,mice
John,12,birds
My Code:
csv_remove("Karen")
Intended File:
Janet,5,cats
Wilson,67,dogs
John,12,birds
However, when I execute my code, I get weird newlines everywhere.
Janet,5,cats
Wilson,67,dogs
John,12,birds
Here is the full code:
def csv_remove(name):
element_list = []
with open(csv_path, 'r') as j:
csv_file = csv.reader(j)
for row in csv_file:
element_list.append(row)
if row[0] == name:
element_list.remove(row)
with open(csv_path, 'w') as j:
csv_file = csv.writer(j)
csv_file.writerows(element_list)
csv_remove("Karen")
Read the documentation. When opening a file for writing using the csv-module you need to
supply newline="":
Source: https://docs.python.org/3/library/csv.html#csv.writer
csv.writer(csvfile, dialect='excel', **fmtparams)
Return a writer object responsible for converting the user’s data into delimited strings on the given file-like object. csvfile can be any object with a write() method. If csvfile is a file object, it should be opened with newline=''
The csv-module handles newlines itself. If you do not specify newline='' for the opened file, it will muck up the line endings and you end up with empty lines in it.
Related
I'm trying to read sentences in a csv file, convert them to lowercase and save in other csv file.
import csv
import pprint
with open('dataset_elec_4000.csv') as f:
with open('output.csv', 'w') as ff:
data = f.read()
data = data.lower
writer = csv.writer(ff)
writer.writerow(data)
but I got error "_csv.Error: sequence expected". What should I do?
*I'm a beginner. Please be nice to me:)
You need to read over your input CSV row-by-row, and for each row, transform it, then write it out:
import csv
with open('output.csv', 'w', newline='') as f_out:
writer = csv.writer(f_out)
with open('dataset_elec_4000.csv', newline='') as f_in:
reader = csv.reader(f_in)
# comment these two lines if no input header
header = next(reader)
writer.writerow(header)
for row in reader:
# row is sequence/list of cells, so...
# select the cell with your sentence, I'm presuming it's the first cell (row[0])
data = row[0]
data = data.lower()
# need to put data back into a "row"
out_row = [data]
writer.writerow(out_row)
Python contains a module called csv for the handling of CSV files. The reader class from the module is used for reading data from a CSV file. At first, the CSV file is opened using the open() method in ‘r’ mode(specifies read mode while opening a file) which returns the file object then it is read by using the reader() method of CSV module that returns the reader object that iterates throughout the lines in the specified CSV document.
import csv
# opening the CSV file
with open('Giants.csv', mode ='r')as file:
# reading the CSV file
csvFile = csv.reader(file)
# displaying the contents of the CSV file
for lines in csvFile:
print(lines)
My csv file has the semicolon as delimiter. I can open it with
r = csv.reader(infile, delimiter=";")
without any issues. The problem is that I want to open the file as a dict. The csv.DictReader class doesn't have the delimiter option.
My code:
import os
import csv
fields = ["Buchungstag", "Buchungstext", "Beguenstigter/Zahlungspflichtiger", "", "", "Betrag", "Verwendungszweck"]
with open("bank.csv") as infile, open("temp2.csv", "w", newline="") as outfile:
r = csv.DictReader(infile)
w = csv.DictWriter(outfile, fields, extrasaction="ignore")
w.writeheader()
for row in r:
w.writerow(row)
I tried opening the file and only loading certain fields, which works if I modify the file beforehand, replacing the ; with , (I used notepad++ for this) – but I would like to skip this part and have the file directly opened.
Both DictReader and DictWriter accept arbitrary arguments including delimiter, and pass them through to the underlying reader or writer object, as the documentation says:
class csv.DictReader(…)
All other optional or keyword arguments are passed to the underlying reader instance.
class csv.DictWriter(…)
Any other optional or keyword arguments are passed to the underlying writer instance.
Changing the relevant line in your code above to
r = csv.DictReader(infile, delimiter=";")
should work as expected.
I have a csv file and I want to transfer the raw data without the headers to a new csv file and have the rows and columns the same as the original.
IRIS_data = "IRIS_data.csv"
with open(IRIS_data, 'wb') as data:
wr = csv.writer(data, quoting=csv.QUOTE_ALL)
with open(IRIS) as f:
next(f)
for line in f:
wr.writerow(line)
The code above is my most recent attempt, when I try run it I get the following error:
a bytes-like object is required, not 'str'
It's because you opened the input file with with open(IRIS_data, 'wb'), which opens it in binary mode, and the output file with just with open(IRIS) which opens it in text mode.
In Python 3, you should open both files in text mode and specify newline='' option)—see the examples in the csv module's documentation)
To fix it, change them as follows:
with open(IRIS_data, 'w', newline='') as data:
and
with open(IRIS, newline='') as f:
However there are other issues with you code. Here's how to use those statements to get what I think you want:
import csv
IRIS = "IRIS.csv"
IRIS_data = "IRIS_data.csv"
with open(IRIS, 'r', newline='') as f, open(IRIS_data, 'w', newline='') as data:
next(f) # Skip over header in input file.
writer = csv.writer(data, quoting=csv.QUOTE_ALL)
writer.writerows(line.split() for line in f)
Contents of IRIS_data.csv file after running the script with your sample input data:
"6.4","2.8","5.6","2.2","2"
"5","2.3","3.3","1","1"
"4.9","2.5","4.5","1.7","2"
"4.9","3.1","1.5","0.1","0"
"5.7","3.8","1.7","0.3","0"
"4.4","3.2","1.3","0.2","0"
"5.4","3.4","1.5","0.4","0"
"6.9","3.1","5.1","2.3","2"
"6.7","3.1","4.4","1.4","1"
"5.1","3.7","1.5","0.4","0"
You have to encode the line you are writing like this:
wr.writerow( line.encode(”utf8”))
Also open your file using open(..., ‘wb’). This will open the file in binary mode. So you are certain the file is actually open in binary mode. Indeed it is better to now explicitly the encoding than assuming it. Enforcing encoding for both reading and writing will save you lots of trouble.
I am trying to create .csv file.
For some reason it skips line before printing entry.
Here is the output
But here is what I need
Below is code. Apparently if line != "": doesn't work
import csv
#-----------------------------------
def csv_writer(data,path):
"""
Write data to a CSV file path
"""
with open(path, "w") as csv_file:
writer = csv.writer(csv_file, delimiter=',')
for line in data:
if line != "":
writer.writerow(line)
#-----------------------------------
if __name__ == "__main__":
data = ["first_name,last_name,city".split(","),
"Tyrese,Hirthe,Strackeport".split(","),
"Jules,Dicki,Lake Nickolasville".split(","),
"Dedric,Medhurst,Stiedemannberg".split(",")
]
path = "output.csv"
csv_writer(data,path)
Some python versions (on windows) have an issue with that with open(path, "w") as csv_file:. A spurious carriage return char is inserted, creating a blank line after each line.
You have to add newline="" as stated in the documentation. Python 3:
with open(path, "w",newline="") as csv_file:
writer = csv.writer(csv_file, delimiter=',')
As for python 2:
with open(path, "wb") as csv_file:
writer = csv.writer(csv_file, delimiter=',')
see also:
portable way to write csv file in python 2 or python 3
csv writer expected byte like and space between rows
(note that latest Python versions on Windows don't need this anymore, but the documentation continues to state it)
When you open the file you need to pass the keyword argument newline with a blank string. This will prevent the newlines being added between rows. Your function should be:
def csv_writer(data,path):
"""
Write data to a CSV file path
"""
with open(path, "w", newline = '') as csv_file:
writer = csv.writer(csv_file, delimiter=',')
for line in data:
if line:
writer.writerow(line)
Note that this is only an issue on Windows.
I am trying to write to a .tsv file using python's CSV module, this is my code so far
file_name = "test.tsv"
TEMPLATE = "template.tsv"
fil = open(file_name, "w")
# Added suggested change
template = csv.DictReader(open(TEMPLATE, 'r'), delimiter='\t')
new_file = csv.DictWriter(fil, fieldnames=template.fieldnames, delimiter='\t')
new_file.writeheader()
basically TEMPLATE is a file that will contain the headers for the file, so i read the headers using DictReader and pass the fieldnames to DictWriter, as far as i know the code is fine, the file test.tsv is being created but for some reason the headers are not being written.
Any help as to why this is happening is appreciated, thanks.
DictReader's first argument should be a file object (create with open()), cf. http://docs.python.org/py3k/library/csv.html#csv.DictReader
You forgot open() for the TEMPLATE file.
import csv
file_name = "test.tsv"
TEMPLATE = "template.tsv"
fil = open(file_name, "w")
# you forgot this line, which will open the file
template_file = open(TEMPLATE, 'r')
template = csv.DictReader(template_file, delimiter='\t')
new_file = csv.DictWriter(fil, fieldnames=template.fieldnames, delimiter='\t')
new_file.writeheader()
Try to give DictReader opened file instead of file name:
csv.DictReader(open(TEMPLATE, 'r'), delimiter='\t')
Same for the writer, but opened for writing.