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How to read a csv file and create a new csv file after every nth number of rows?

I'm trying to write a function that reads a sheet of an existing .csv file and every 20 rows are copied to a newly created csv file. Therefore, it needs to be designed like a file counter "file_01, file_02, file_04,...," where the first 20 rows are copied to file_01, the next 20 to file_02.csv, and so on.
Currently I have this code which hasn't worked for me work so far.
import csv
import os.path
from itertools import islice
N = 20
new_filename = ""
filename = ""
with open(filename, "rb") as file: # the a opens it in append mode
reader = csv.reader(file)
for i in range(N):
line = next(file).strip()
#print(line)
with open(new_filename, 'wb') as outfh:
writer = csv.writer(outfh)
writer.writerow(line)
writer.writerows(islice(reader, 2))
I have attached a file for testing.
https://1drv.ms/u/s!AhdJmaLEPcR8htYqFooEoYUwDzdZbg
32.01,18.42,58.98,33.02,55.37,63.25,12.82,-32.42,33.99,179.53,
41.11,33.94,67.85,57.61,59.23,94.69,19.43,-19.15,21.71,-161.13,
49.80,54.12,72.78,100.74,56.97,128.84,26.95,-6.76,10.07,-142.62,
55.49,81.02,68.93,148.17,49.25,157.32,34.94,5.39,0.44,-123.32,
56.01,112.81,59.27,177.87,38.50,179.63,43.43,18.42,-5.81,-102.24,
50.79,142.87,48.06,-162.32,26.60,-161.21,52.38,34.37,-7.42,-79.64,
41.54,167.36,37.12,-145.93,15.01,-142.84,60.90,57.05,-4.47,-56.54,
30.28,-172.09,27.36,-130.24,5.11,-123.66,66.24,91.12,-0.76,-35.44,
18.64,-153.20,19.52,-114.09,-1.54,-102.96,64.77,131.32,5.12,-21.68,
7.92,-134.07,14.24,-96.93,-3.79,-80.91,57.10,162.35,12.51,-9.21,
-0.34,-113.74,11.80,-78.73,-2.49,-58.46,46.75,-175.86,20.81,2.87,
-4.81,-91.85,11.78,-60.28,0.59,-39.26,35.75,-158.12,29.79,15.71,
-4.76,-68.67,13.79,-43.84,6.82,-24.69,25.27,-141.56,39.05,30.71,
-1.33,-46.42,18.44,-30.23,14.53,-11.95,16.21,-124.45,47.91,50.25,
4.14,-29.61,24.89,-18.02,23.01,0.10,9.59,-106.05,54.46,77.07,
11.04,-15.39,32.33,-6.66,31.92,12.48,6.24,-86.34,55.72,110.53,
18.69,-2.32,40.46,4.57,41.11,26.87,6.07,-65.68,50.25,142.78,
26.94,10.56,49.18,16.67,49.92,45.39,8.06,-46.86,40.13,168.29,
35.80,24.58,58.45,31.99,56.83,70.92,12.96,-31.90,28.10,-171.07,
44.90,41.72,67.41,55.89,59.21,103.94,19.63,-18.67,15.97,-152.40,
-5.41,-77.62,11.40,-63.21,4.80,-29.06,31.33,-151.44,43.00,37.25,
-2.88,-54.38,13.08,-46.00,12.16,-15.86,21.21,-134.62,51.25,59.16,
1.69,-35.73,17.44,-32.01,20.37,-3.78,13.06,-117.10,56.18,88.98,
8.15,-20.80,23.70,-19.66,29.11,8.29,7.74,-98.22,54.91,123.30,
15.52,-7.45,31.04,-8.22,38.22,21.78,5.76,-77.99,47.34,153.31,
23.53,5.38,39.07,2.98,47.29,38.71,6.58,-57.45,36.18,176.74,
32.16,18.76,47.71,14.88,55.08,61.71,9.76,-40.52,23.99,-163.75,
41.27,34.36,56.93,29.53,59.23,92.75,15.53,-26.40,12.16,-145.27,
49.92,54.65,66.04,51.59,57.34,126.97,22.59,-13.65,2.14,-126.20,
55.50,81.56,72.21,90.19,49.88,155.84,30.32,-1.48,-4.71,-105.49,
55.92,113.45,70.26,139.40,39.23,178.48,38.55,10.92,-7.09,-83.11,
50.58,143.40,61.40,172.50,27.38,-162.27,47.25,24.86,-4.77,-60.15,
41.30,167.74,50.34,-166.33,15.74,-143.93,56.21,43.14,-0.54,-38.22,
30.03,-171.78,39.24,-149.48,5.71,-124.87,63.77,70.19,4.75,-24.15,
18.40,-152.91,29.17,-133.78,-1.18,-104.31,66.51,108.81,11.86,-11.51,
7.69,-133.71,20.84,-117.74,-3.72,-82.28,61.95,146.15,20.05,0.65,
-0.52,-113.33,14.97,-100.79,-2.58,-59.75,52.78,172.46,28.91,13.29,
-4.91,-91.36,11.92,-82.84,0.34,-40.12,41.93,-167.91,38.21,27.90,

These are some of the problems with your current solution.
You created a csv.reader object but then you did not use it
You read each line but then you did not store them anywhere
You are not keeping track of 20 rows which was supposed to be your requirement
You created the output file in a separate with block which does not have access anymore to the read lines or the csv.reader object
Here's a working solution:
import csv
inp_file = "input.csv"
out_file_pattern = "file_{:{fill}2}.csv"
max_rows = 20
with open(inp_file, "r") as inp_f:
reader = csv.reader(inp_f)
all_rows = []
cur_file = 1
for row in reader:
all_rows.append(row)
if len(all_rows) == max_rows:
with open(out_file_pattern.format(cur_file, fill="0"), "w") as out_f:
writer = csv.writer(out_f)
writer.writerows(all_rows)
all_rows = []
cur_file += 1
The flow is as follows:
Read each row of the CSV using a csv.reader
Store each row in an all_rows list
Once that list gets 20 rows, open a file and write all the rows to it
Use the csv.writer's writerows method
Use a cur_file counter to format the filename
Every time 20 rows are dumped to a file, empty out the list and increment the file counter
This solution includes the blank lines as part of the 20 rows. Your test file has actually 19 rows of CSV data and 1 row for a blank line. If you need to skip the blank line, just add a simple check of
if not row:
continue
Also, as I mentioned in a comment, I assume that the input file is an actual CSV file, meaning it's a plain text file with CSV formatted data. If the input is actually an Excel file, then solutions like this won't work, because you'll need some special libraries to read Excel files, even if the contents visually looks like CSV or even if you rename the file to .csv.

Without using any special CSV libraries (e.g. csv, though you could, just that I don't know how to use them, however don't think it is necessary for this case), you could:
excel_csv_fp = open(r"<file_name>", "r", encoding="utf-8") # Check proper encoding for your file
csv_data = excel_csv_fp.readlines()
file_counter = 0
new_file_name = ""
new_fp = ""
for line in csv_data:
if line == "":
if new_fp != "":
new_fp.close()
file_counter += 1
new_file_name = "file_" + "{:02d}".format(file_counter) # 1 turns into 01 and 10 turns 10 i.e. remains the same
new_fp = open("<some_path>/" + new_file_name + ".csv", "w", encoding="utf-8") # Makes a new CSV file to start writing to
elif new_fp != "": # Updated code to make sure new_fp is a file pointer and not a string
new_fp.write(line) # Write each line after a space
If you have any questions on any of the code (how it works, why I choose what etc.), just ask in the comments and I'll try to reply as soon as possible.

Writing to CSV file choosing the column to write in

I'm trying to import the data from X (6 in this case) CSV Files containing some data about texts, and putting one specific row from each Document onto a new one, in such a way that they appear next to each other (export from document 1 on column 1, from the second document on row 2 and so on). I've been unsuccessful so far.
# I have a list containing the path to all relevant files
files = ["path1", "path2", ...]
# then I tried cycling through the folder like this
for file in files:
with open(file, "r") as csvfile:
reader = csv.reader(csvfile, delimiter=",")
for row on reader:
# I'm interested in the stuff stored on Column 2
print([row[2]])
# as you can see, I can get the info from the files, but from here
# on, I can't find a way to then write that information on the
# appropiate coloumn of the newly created CSV file
I know how to open a writer, what I don't know is how to write a script that writes the info it fetches from the original 6 documents on a DIFFERENT COLUMN every time a new file is processed.

# I have a list containing the path to all relevant files
files = ["path1", "path2", ...]
newfile = "newpath1"
# then I tried cycling through the folder like this
for file in files:
with open(file, "r") as csvfile:
reader = csv.reader(csvfile, delimiter=",")
with open(newfile, "a") as wcsvfile:
writer = csv.writer(wcsvfile)
for row on reader:
# I'm interested in the stuff stored on Column 2
writer.writerow([row[2]])

Updating a specific csv column based on randomname

My code pulls a random name from a csv file. When a button is pressed i want my code to search through the csv file, and update the cell next to the name generated previously in the code.
The variable in which the name is stored in is called name
The index which pulls the random name from the csv file is stored in the variable y
The function looks like this. I have asked this question previously however have had no luck in receiving answers, so i have made edits to the function and hopefully made it more clear.
namelist_file = open('StudentNames&Questions.csv')
reader = csv.reader(namelist_file)
writer = csv.writer(namelist_file)
rownum=0
array=[]
for row in reader:
if row == name:
writer.writerow([y], "hello")
Only the first two columns of the csv file are relevant
This is the function which pulls a random name from the csv file.
def NameGenerator():
namelist_file = open('StudentNames&Questions.csv')
reader = csv.reader(namelist_file)
rownum=0
array=[]
for row in reader:
if row[0] != '':
array.append(row[0])
rownum=rownum+1
length = len(array)-1
i = random.randint(1,length)
global name
name = array[i]
return name

There are a number of issues with your code:
You're trying to have both a reader object and a writer on the same file at the same time. Instead, you should read the file contents in, make any changes necessary and then write the whole file back out at the end.
You need to open the file in write mode in order to actually make changes to the contents. Currently, you don't specify what mode you're using so it defaults to read mode.
row is actually a list representing all data in the row. Therefore, it cannot be equal to the name you're searching, only the 0th index might be.
The following should work:
with open('StudentNames&Questions.csv', 'r') as infile:
reader = csv.reader(infile)
data = [row for row in reader]
for row in data:
if row[0] == name:
row[1] += 1
with open('StudentNames&Questions.csv', 'w', newline='') as outfile:
writer = csv.writer(outfile)
writer.writerows(data)

Python - How to read previous lines while reading csv file?

I want to read rows in excel table but when I want, during reading process, I would like to stop reading forward and I want to read previous lines (backward reading)? How can I go previous rows again?
import csv
file = open('ff.csv2', 'rb')
reader = csv.reader(file)
for row in reader:
print row

You could always store the lines in a list and then access each line using the index.
import csv
file = open('ff.csv2', 'r')
def somereason(line):
# some logic to decide if stop reading by returning True
return False # keep on reading
for row in csv.reader(file):
if somereason(line):
break
lines.append(line)
# visit the stored lines in reverse
for row in reversed(lines):
print(row)

Loop retrieve data from csv, append to file

I have created a Python 2.7 script that does the following:
Gets a list of filenames from a folder, and writes them to a csv file, one for each row.
And
Enters data into a search box on the web.
Writes the result from the search box into another csv file.
So what I would like now, is for the csv data in (1 ) to act as the input for (2 ).
i.e. for each filename in the csv file, it conducts a search for that cell.
Additionally, instead of just writing the results into a second csv file in (3 ), I would like to append the result into the first csv file – OR generate a new one with both columns.
I can provide the code, but since it's 50 lines already, I've just tried to keep this question descriptive.
Update: Proposed retrieval and append:
with open("file.csv","a+") as f:
r = csv.reader(f)
wr = csv.writer(f, delimiter="\n")
result = []
for line in r:
searchbox = driver.find_element_by_name("searchbox")
searchbox.send_keys(line)
sleep(8)
search_reply = driver.find_element_by_class_name("search_reply")
result = re.findall("((?<=\()[0-9]*)", search_reply.text)
wr.writerow(result)

Open for reading and appending, store the output then write at the end:
import csv
with open("first.csv","a+") as f:
r = csv.reader(f)
wr = csv.writer(f,delimiter="\n")
result = []
for line in r:
# process lines/step 2
# append to result
wr.writerow(result)