Replace particular string in csv python in a particular row and column - python

I have looked around but didnt quite find what i have problems with.
The question i have about is that in the csv files called registro_usuarios.csv that has the following data. Which has 6 rows and 6 colmuns
registro_usuarios.csv:
RUT,Name,LastName,E-mail,ISBN1,ISBN2
111,Pablo1,Alar1,mail1,0,0
222,Pablo2,Alar2,mail2,0,0
333,Pablo3,Alar3,mail3,0,0
444,Pablo4,Alar4,mail4,0,0
555,Pablo5,Alar5,mail5,0,0
Now how do can i make a def that allows me to replace a 0 below ISBN1 or ISBN2 for a given RUT?... For example, i want to replace the ISBN1 of the rut 333 for 777. Then after using the def, it should change the data in the csv like this. since rows and columns starts with 0,0 i believe then ISBN1 of the rut 333 is row 3 column 5 if im not mistaken.
registro_usuarios.csv:
RUT,Nombre,Apellido,E-mail,ISBN1,ISBN2
111,Pablo1,Alar1,mail1,0,0
222,Pablo2,Alar2,mail2,0,0
333,Pablo3,Alar3,mail3,777,0
444,Pablo4,Alar4,mail4,0,0
555,Pablo5,Alar5,mail5,0,0

This is the simplest way I could think of:
>>> import csv
>>> with open('data.csv') as f:
... data = [r for r in csv.reader(f)]
...
>>> data[3][4] = '777'
>>> with open('data.csv', 'w') as f:
... csv.writer(f).writerows(data)
...
As you mentioned you want to alter a row with an specific RUT. In that case I would use DictReader/DictWriter and a function to change the row based on the RUT:
import csv
def change_by_rut(csv_data, rut, new_isbn1):
for row in csv_data:
if row['RUT'] == rut:
row['ISBN1'] = new_isbn1
with open('data.csv') as f:
data = [r for r in csv.DictReader(f)]
change_by_rut(data, '333', '777')
with open('data.csv', 'w') as f:
writer_obj = csv.DictWriter(f, fieldnames=data[0].keys())
writer_obj.writeheader()
writer_obj.writerows(data)

You could use pandas too:
# recreate file
from pathlib import Path
Path('temp.txt').write_text("""RUT,Name,LastName,E-mail,ISBN1,ISBN2
111,Pablo1,Alar1,mail1,0,0
222,Pablo2,Alar2,mail2,0,0
333,Pablo3,Alar3,mail3,0,0
444,Pablo4,Alar4,mail4,0,0
555,Pablo5,Alar5,mail5,0,0""")
import pandas as pd
df = pd.read_csv('temp.txt', index_col=0)
df.loc[333,'ISBN1'] = 777
print(df)
# export example
df.to_csv('temp2.txt')

Related

How to delete a row in a CSV file if a cell is empty using Python

I want to go through large CSV files and if there is missing data I want to remove that row completely, This is only row specific so if there is a cell that = 0 or has no value then I want to remove the entire row. I want this to happen for all the columns so if any column has a black cell it should delete the row, and return the corrected data in a corrected csv.
import csv
with open('data.csv', 'r') as csvfile:
csvreader = csv.reader(csvfile)
for row in csvreader:
print(row)
if not row[0]:
print("12")
This is what I found and tried but it doesnt not seem to be working and I dont have any ideas about how to aproach this problem, help please?
Thanks!
Due to the way in which CSV reader presents rows of data, you need to know how many columns there are in the original CSV file. For example, if the CSV file content looks like this:
1,2
3,
4
Then the lists return by iterating over the reader would look like this:
['1','2']
['3','']
['4']
As you can see, the third row only has one column whereas the first and second rows have 2 columns albeit that one is (effectively) empty.
This function allows you to either specify the number of columns (if you know them before hand) or allow the function to figure it out. If not specified then it is assumed that the number of columns is the greatest number of columns found in any row.
So...
import csv
DELIMITER = ','
def valid_column(col):
try:
return float(col) != 0
except ValueError:
pass
return len(col.strip()) > 0
def fix_csv(input_file, output_file, cols=0):
if cols == 0:
with open(input_file, newline='') as indata:
cols = max(len(row) for row in csv.reader(indata, delimiter=DELIMITER))
with open(input_file, newline='') as indata, open(output_file, 'w', newline='') as outdata:
writer = csv.writer(outdata, delimiter=DELIMITER)
for row in csv.reader(indata, delimiter=DELIMITER):
if len(row) == cols:
if all(valid_column(col) for col in row):
writer.writerow(row)
fix_csv('original.csv', 'fixed.csv')
maybe like this
import csv
with open('data.csv', 'r') as csvfile:
csvreader = csv.reader(csvfile)
data=list(csvreader)
data=[x for x in data if '' not in x and '0' not in x]
you can then rewrite the the csv file if you like
Instead of using csv, you should use Pandas module, something like this.
import pandas as pd
df = pd.read_csv('file.csv')
print(df)
index = 1 #index of the row that you want to remove
df = df.drop(index)
print(df)
df.to_csv('file.csv')

Split values in CSV that look like JSON

So I have a CSV file with a column called content. However, the contents in column look like it is based on JSON, and, therefore, house more columns. I would like to split these contents into multiple columns or extract the final part of it after "value". See picture below to see an example of the file. Any ideas how to get this? I would prefer using Python. I don't have any experience with JSON.
Using pandas you could do in a simpler way.
EDIT updated to handle the single quotes:
import pandas as pd
import json
data = pd.read_csv('test.csv', delimiter="\n")["content"]
res = [json.loads(row.replace("'", '"')) for row in data]
result = pd.DataFrame(res)
result.head()
# Export result to CSV
result.to_csv("result.csv")
my csv:
result:
This script will create a new csv file with the 'value' added to the csv as an additional column
(make sure that the input_csv and output_csv are different filenames)
import csv
import json
input_csv = "data.csv"
output_csv = "data_updated.csv"
values = []
with open(input_csv) as f_in:
dr = csv.DictReader(f_in)
for row in dr:
value = json.loads(row["content"].replace("'", '"'))["value"]
values.append(value)
with open(input_csv) as f_in:
with open(output_csv, "w+") as f_out:
w = csv.writer(f_out, lineterminator="\n")
r = csv.reader(f_in)
all = []
row = next(r)
row.append("value")
all.append(row)
i = 0
for row in r:
row.append(values[i])
all.append(row)
i += 1
w.writerows(all)

How to get specific columns in a certain range from a csv file without using pandas

For some reason the pandas module does not work and I have to find another way to read a (large) csv file and have as Output specific columns within a certain range (e.g. first 1000 lines). I have the code that reads the entire csv file, but I haven't found a way to display just specific columns.
Any help is much appreciated!
import csv
fileObj = open('apartment-data-all-4-xaver.2018.csv')
csvReader = csv.reader( fileObj )
for row in csvReader:
print row
fileObj.close()
I created a small csv file with the following contents:
first,second,third
11,12,13
21,22,23
31,32,33
41,42,43
You can use the following helper function that uses namedtuple from collections module, and generates objects that allows you to access your columns like attributes:
import csv
from collections import namedtuple
def get_first_n_lines(file_name, n):
with open(file_name) as file_obj:
csv_reader = csv.reader(file_obj)
header = next(csv_reader)
Tuple = namedtuple('Tuple', header)
for i, row in enumerate(csv_reader, start=1):
yield Tuple(*row)
if i >= n: break
If you want to print first and third columns, having n=3 lines, you use the method like this (Python 3.6 +):
for line in get_first_n_lines(file_name='csv_file.csv', n=3):
print(f'{line.first}, {line.third}')
Or like this (Python 3.0 - 3.5):
for line in get_first_n_lines(file_name='csv_file.csv', n=3):
print('{}, {}'.format(line.first, line.third))
Outputs:
11, 13
21, 23
31, 33
use csv dictreader and then filter out specific rows and columns
import csv
data = []
with open('names.csv', newline='') as csvfile:
reader = csv.DictReader(csvfile)
for row in reader:
data.append(row)
colnames = ['col1', 'col2']
for i in range(1000):
print(data[i][colnames[0]], data[i][colnames[1]])

Remove row from CSV that contains empty cell using Python

I am splitting a CSV file based on a column with dates into separate files. However, some rows do contain a date but the others cells are empty. I want to remove these rows that contain empty cells from the CSV. But I'm not sure how to do this.
Here's is my code:
csv.field_size_limit(sys.maxsize)
with open(main_file, "r") as fp:
root = csv.reader(fp, delimiter='\t', quotechar='"')
result = collections.defaultdict(list)
next(root)
for row in root:
year = row[0].split("-")[0]
result[year].append(row)
for i,j in result.items():
row_count = sum(1 for row in j)
print(row_count)
file_path = "%s%s-%s.csv"%(src_path, i, row_count)
with open(file_path, 'w') as fp:
writer = csv.writer(fp, delimiter='\t', quotechar='"')
writer.writerows(j)
Pandas is perfect for this, especially if you want this to be easily adjusted to, say, other file formats. Of course one could consider it an overkill.
To just remove rows with empty cells:
>>> import pandas as pd
>>> data = pd.read_csv('example.csv', sep='\t')
>>> print data
A B C
0 1 2 5
1 NaN 1 9
2 3 4 4
>>> data.dropna()
A B C
0 1 2 5
2 3 4 4
>>> data.dropna().to_csv('example_clean.csv')
I leave performing the splitting and saving into separate files using pandas as an exercise to start learning this great package if you want :)
This would skip all all rows with at least one empty cell:
with open(main_file, "r") as fp:
....
for row in root:
if not all(map(len, row)):
continue
Pandas is Best in Python for handling any type of data processing.For help you can go through on link :- http://pandas.pydata.org/pandas-docs/stable/10min.html

How to perform a simple calculation in a CSV and append the results to the file

I have a csv which contains 38 colums of data, all I want to find our how to do is, divide column 11 by column by column 38 and append this data tot he end of each row. Missing out the title row of the csv (row 1.)
If I am able to get a snippet of code that can do this, I will be able to manipulate the same code to perform lots of similar functions.
My attempt involved editing some code that was designed for something else.
See below:
from collections import defaultdict
class_col = 11
data_col = 38
# Read in the data
with open('test.csv', 'r') as f:
# if you have a header on the file
# header = f.readline().strip().split(',')
data = [line.strip().split(',') for line in f]
# Append the relevant sum to the end of each row
for row in xrange(len(data)):
data[row].append(int(class_col)/int(data_col))
# Write the results to a new csv file
with open('testMODIFIED2.csv', 'w') as nf:
nf.write('\n'.join(','.join(row) for row in data))
Any help will be greatly appreciated. Thanks SMNALLY
import csv
with open('test.csv', 'rb') as old_csv:
csv_reader = csv.reader(old_csv)
with open('testMODIFIED2.csv', 'wb') as new_csv:
csv_writer = csv.writer(new_csv)
for i, row in enumerate(csv_reader):
if i != 0:
row.append(float(row[10]) / float(row[37]))
csv_writer.writerow(row)
Use pandas:
import pandas
df = pandas.read_csv('test.csv') #assumes header row exists
df['FRACTION'] = 1.0*df['CLASS']/df['DATA'] #by default new columns are appended to the end
df.to_csv('out.csv')

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