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)
Related
from operator import itemgetter
COLS = 15,21,27
COLS1 = 16,22,28
filename = "result.csv"
getters = itemgetter(*(col-1 for col in COLS))
getters1 = itemgetter(*(col-1 for col in COLS1))
with open('result.csv', newline='') as csvfile:
for row in csv.reader(csvfile):
row = zip(getters(row))
for row1 in csv.reader(csvfile):
row1 = zip(getters1(row1))
print(row)
print(row1)
with open('results1.csv', "w", newline='') as f:
fieldnames = ['AAA','BBB']
writer = csv.writer(f,delimiter=",")
for row in row:
writer.writerow(row)
writer.writerow(row1)
I am getting a NameError: name 'row1' is not defined error. I want to write each of the COLS in a separate column in the results1 file. How would I go about this?
So, there are few things going on in the code that are potentially leading to errors.
First is the way csv.reader(csvfile) works in python. When reading the file with csv.reader it basically scans the next line in the file when called and returns it. The csv part in this case simply uses the .cvs format and returns the data in a list, rather than a simple string of text in the standard python file reader. This is fine for a lot of use cases, but the issue here we are running into, is that when you run:
for row in csv.reader(csvfile):
row = zip(getters(row))
the csv.reader(csvfile) gets called for every row in the entire file and the for loop only stops when it runs out of data in the "results.csv" file. Meaning, if you want to use the data from each row, you need to store it in some way before running out the file. I think that's what you are trying to achieve with row = zip(getters(row)) but the issue here is row is both being assigned to zip(getters(row)) and being used as the variable in the for loop. Since you are essentially calling csv.reader, returning to variable row, then reassigning row to being zip(getters(row)), you are just writing over the variable row every iteration of the for loop and the result is nothing gets stored.
In order to store your csv data, try this:
data = [[]]
for row in csv.reader(csvfile):
temp = zip(getters(row))
data.append(temp)
This will store your row in a list called data.
Then, the second error is the one you are asking about, which is row1 not being defined. This happened in your code because the for loop ran through every row in the csv file. When you then call csv.reader again in the second for loop it can't read anything because the first for loop already read through the entire csv file and it doesn't know to start over at the beginning of the file. Therefore, row1 never gets declared or assigned, and therefore when you call again it in writer.writerow(row1), row1 doesn't exist.
There a couple ways to fix this. You could close the file, reopen it again and start from the beginning of the file again. Or you could store it at the same time in the first for loop. So like this:
data = [[]]
data1 = [[]]
for row in csv.reader(csvfile):
temp = zip(getters(row))
data.append(temp)
temp2 = zip(getters1(row))
data2.append(temp2)
Now you will have 3 columns of data in both data and data1.
Now for writing to the "results1.csv" file. Here you used row as the for loop variable as well as the iterable to run through, which does not work. Also, you call writer.writerow(row) then writer.writerow(row1), which also doesn't work. Try this instead:
with open('results1.csv', "w", newline='') as f:
writer = csv.writer(f,delimiter=",")
for row in range(len(data)):
writer.writerow(data[row] + data1[row])
Now it also looks like you want to add headers for each column in fieldnames = ['AAA','BBB'] . Unfortunetly, csv.writer does not have an easy way to do this, instead csv.DictWriter and writer.writeheader() must be used first.
with open('results1.csv', "w", newline='') as f:
fieldnames = ['A','A','A','B','B','B']
writer = csv.DictWriter(f,delimiter=",", fieldnames=fieldnames)
writer.writeheader()
writer = csv.writer(f,delimiter=",")
for row in range(len(data)):
writer.writerow(data[row] + data1[row])
Hope this helps!
I have a code like this:
with data_from_db(vars(args), sql_query) as row_source:
build_csv(csv_filename, row_source)
Which call the following function:
def build_csv(filename, row_source):
with open(filename, "w", newline="", encoding="utf-8") as csv_file:
fixed = 'PINCARD'
writer = csv.writer(csv_file, delimiter=";")
for row in row_source:
writer.writerow(row)
This code will get data from a database (query is saved on a external file) and will create a CSV file with two columns. However, I need to add an extra column with a fixed value on every single row, and that column must be the first one.
The current output is:
value1;value2
I need
PINCARD;value1;value2
However, I cannot figure out how to do that. Sorry for my lack of knowledge.
I need to overwrite a random row of a csv file, with a row from another csv file in Python.
It will be ok even if the random row is deleted, and the new row is written at the end of the csv file.
My code is:
with open("cache.csv", "r+") as cache_csv:
writer = csv.writer(cache_csv)
leggi = csv.reader(cache_csv)
leggi_list = list(leggi)[1:]
with open('/content/drive/MyDrive/Colab Notebooks/size.csv') as f:
reader = csv.reader(f)
Then
for row in reader:
if self.cache_max-self.observation < int(row[1]):
for compare_row in leggi_list:
if compare_row[0] != row[0]:
#add code here that I need
I tried with:
if compare_row[0] != row[0]:
riga = random.choice(leggi_list)
writer.writerow(row, riga)
so, take one random row and 'overwrite' it with row, but it's wrong.
I don't know how to do that.
Can someone help me ?
Thank you .
I am new to Python and I attempt to read .csv files sequentially in a for or while loop (I have about 250 .csv). The aim is to read each .csv file and isolate only all the columns, whenever a specific column (let's call it "wanted_column") is non-empty (i.e. its non-empty rows). Then, save all the non-empty rows of the "wanted_column", as well as all its columns, in a new .csv file.
Hence, at the end, I want to have 250 .csv files with all columns for each row that has non-empty elements in the "wanted_column".
Hopefully this is clear. I would appreciate any ideas.
George
I wrote this code below just to give you an idea of how to do it. Beware that this code below does not check for any errors. Its behavior is undefined if one of your CSV files is empty, if it couldn't find the file, and if the column you defined is a none existence column in one of the file. There could be more. Thus, you would want to build a check code around it. Also, your CSV formatting could greatly be depended on python csv package.
So now to the code explanation. For the "paths" variable. You can give that a string, a tuple, or a list. If you give it a string, it will convert that to a tuple with one index. You can give that variable the file(s) that you want to work with.
For the "column" variable, that one should be a string. You need to build an error checking for that if needed.
For code routines, the function will read all the CSV files of the paths list. Each time it read a file, it will read the first line first and save the content to a variable(rowFields).
After that, it generates the dict header(fields) with key(column name) to value(position). That dict is used to search for the column position by using its name. For here, you could also go through each field and if the field matches the column name then you save that value as the column position. Then that position could later be used instead of keep on searching the dict for the position using the name. The later method described in this paragraph should be the fastest.
After that, it goes on and read each row of the CSV file until the end. Each time it read a row, it will check if the length of the string from the column that defined by the "column" variable is larger than zero. If that string length is larger than zero, then it will append that row to the variable contentRows.
After the function done reading the CSV file, it will write the contents of variable "rowFields" and "contentRows" to a CSV file that defined by the "outfile" variable. To make it easy for me, outfile simply equal to input file + ".new". You can just change that.
import csv
def getNoneEmpty( paths, column ):
if isinstance(paths, str):
paths = (paths, )
if not isinstance(paths, list) and not isinstance(paths, tuple):
raise("paths have to be a or string, list, or tuple")
quotechar='"'
delimiter=","
lineterminator="\n"
for f in paths:
outfile = f + ".new" # change this area to how you want to generate the new file
fields = {}
rowFields = None
contentRows = []
with open(f, newline='') as csvfile:
csvReader = csv.reader(csvfile, delimiter=delimiter, quotechar=quotechar, lineterminator=lineterminator)
rowFields = next(csvReader)
for i in range(0, len(rowFields)):
fields[rowFields[i]] = i
for row in csvReader:
if len(row[fields[column]]) != 0:
contentRows.append(row)
with open(outfile, 'w') as csvfile:
csvWriter = csv.writer(csvfile,delimiter=delimiter, quotechar=quotechar,quoting=csv.QUOTE_MINIMAL, lineterminator=lineterminator)
csvWriter.writerow(rowFields)
csvWriter.writerows(contentRows)
getNoneEmpty(["test.csv","test2.csv"], "1958")
test.csv content:
"Month","1958","1959","1960"
"JAN",115,360,417
"FEB",318,342,391
"MAR",362,406,419
"APR",348,396,461
"MAY",11,420,472
"JUN",124,472,535
"JUL",158,548,622
"AUG",505,559,606
"SEP",404,463,508
"OCT",,407,461
"NOV",310,362,390
"DEC",110,405,432
test2.csv content:
"Month","1958","1959","1960"
"JAN",,360,417
"FEB",318,342,391
"MAR",362,406,419
"APR",348,396,461
"MAY",,420,472
"JUN",,472,535
"JUL",,548,622
"AUG",505,559,606
"SEP",404,463,508
"OCT",,407,461
"NOV",310,362,390
"DEC",110,405,432
Hopefully it will work:
def main():
temp = []
with open(r'old_csv') as csv_file:
csv_reader = csv.reader(csv_file, delimiter=';')
for row in csv_reader:
for x in row:
temp.append(x)
with open(r'new_csv', mode='w') as new_file:
writer = csv.writer(new_file, delimiter=',', lineterminator='\n')
for col in temp:
list_ = col.split(',')
writer.writerow(list_)
I have been trying initially to create a program to go through one file and select certain columns that will then be moved to a new text file. So far I have
import os, sys, csv
os.chdir("C://Users//nelsonj//Desktop//Master_Project")
with open('CHS_2009_test.txt', "rb") as sitefile:
reader = csv.reader(sitefile, delimiter=',')
pref_cols = [0,1,2,4,6,8,10,12,14,18,20,22,24,26,30,34,36,40]
for row in reader:
new_cols = list(row[i] for i in pref_cols)
print new_cols
I have been trying to use the csv functions to write the new file but I am continuosly getting errors. I will eventually need to do this over a folder of files, but thought I would try to do it on one before tackling that.
Code I attempted to use to write this data to a new file
for row in reader:
with open("CHS_2009_edit.txt", 'w') as file:
new_cols = list(row[i] for i in pref_cols)
newfile = csv.writer(file)
newfile.writerows(new_cols)
This kind of works in that I get a new file, but in only prints the second row of values from my csv, i.e., not the header values and places commas in between each individual character, not just copying over the original columns as they were.
I am using PythonWin with Python 2.6(from ArcGIS)
Thanks for the help!
NEW UPDATED CODE
import os, sys, csv
path = ('C://Users//nelsonj//Desktop//Master_Project')
for filename in os.listdir(path):
pref_cols = [0,1,2,4,6,8,10,12,14,18,20,22,24,26,30,34,36,40]
with open(filename, "rb") as sitefile:
with open(filename.rsplit('.',1)[0] + "_Master.txt", 'w') as output_file:
reader = csv.reader(sitefile, delimiter=',')
writer = csv.writer(output_file)
for row in reader:
new_row = list(row[i] for i in pref_cols)
writer.writerow(new_row)
print new_row
Getting list index out of range for the new_row, but it seems to still be processing the file. Only thing I can't get it to do now is loop through all files in my directory. Here's a hyperlink to Screenshot of data text file
Try this:
new_header = list(row[i] for i in pref_cols if i in row)
That should avoid the error, but it may not avoid the underlying problem. Would you paste your CSV file somewhere that I can access, and I'll fix this for you?
For your purpose of filtering, you don't have to treat the header differently from the rest of the data. You can go ahead remove the following block:
headers = reader.next()
for row in headers:
new_header = list(row[i] for i in pref_cols)
print new_header
Your code did not work because you treated headers as a list of rows, but headers is just one row.
Update
This update deals with writing the CSV data to a new file. You should move the open statement above the for row...
with open("CHS_2009_edit.txt", 'w') as output_file:
writer = csv.writer(output_file)
for row in reader:
new_cols = list(row[i] for i in pref_cols)
writer.writerows(new_cols)
Update 2
This update deals with the header output problem. If you followed my suggestions, you should not have this problem. I don't know what your current code looks like, but it looks like you supplies a string where the code expects a list. Here is the code that I tried on my system (using my made-up data) and it seems to work:
pref_cols = [...] # <<=== Should be set before entering the loop
with open('CHS_2009_test.txt', "rb") as sitefile:
with open('CHS_2009_edit.txt', 'w') as output_file:
reader = csv.reader(sitefile, delimiter=',')
writer = csv.writer(output_file)
for row in reader:
new_row = list(row[i] for i in pref_cols)
writer.writerow(new_row)
One thing to notice: I use writerow() to write a single row, where you use writerows() -- that makes a difference.