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I am new to python. I have a .csv file which has 13 columns. I want to round off the floating values of the 2nd column which I was able to achieve successfully. I did this and stored it in a list. Now I am unable to figure out how to overwrite the rounded off values into the same csv file and into the same column i.e. column 2? I am using python3. Any help will be much appreciated.
My code is as follows:
Import statements for module import:
import csv
Creating an empty list:
list_string = []
Reading a csv file
with open('/home/user/Desktop/wine.csv', 'r') as csvDataFile:
csvReader = csv.reader(csvDataFile, delimiter = ',')
next(csvReader, None)
for row in csvReader:
floatParse = float(row[1])
closestInteger = int(round(floatParse))
stringConvert = str(closestInteger)
list_string.append(stringConvert)
print(list_string)
Writing into the same csv file for the second column (Overwrites the entire Excel file)
with open('/home/user/Desktop/wine.csv', 'w') as csvDataFile:
writer = csv.writer(csvDataFile)
next(csvDataFile)
row[1] = list_string
writer.writerows(row[1])
PS: The writing into the csv overwrites the entire csv and removes all the other columns which I don't want. I just want to overwrite the 2nd column with rounded off values and keep the rest of the data same.
this might be what you're looking for.
import pandas as pd
import numpy as np
#Some sample data
data = {"Document_ID": [102994,51861,51879,38242,60880,76139,76139],
"SecondColumnName": [7.256,1.222,3.16547,4.145658,4.154656,6.12,17.1568],
}
wine = pd.DataFrame(data)
#This is how you'd read in your data
#wine = pd.read_csv('/home/user/Desktop/wine.csv')
#Replace the SecondColumnName with the real name
wine["SecondColumnName"] = wine["SecondColumnName"].map('{:,.2f}'.format)
#This will overwrite the sheet, but it will have all the data as before
wine.to_csv(/home/user/Desktop/wine.csv')
Pandas is way easier than read csv...I'd recommended checking it out.
I think this better answers the specific question. The key to this is to define an input_file and an output_file during the with part.
The StringIO part is just there for sample data in this example. newline='' is for Python 3. Without it, blank lines between each row appears in the output. More info.
import csv
from io import StringIO
s = '''A,B,C,D,E,F,G,H,I,J,K,L
1,4.4343,3,4,5,6,7,8,9,10,11
1,8.6775433,3,4,5,6,7,8,9,10,11
1,16.83389832,3,4,5,6,7,8,9,10,11
1,32.2711122,3,4,5,6,7,8,9,10,11
1,128.949483,3,4,5,6,7,8,9,10,11'''
list_string = []
with StringIO(s) as input_file, open('output_file.csv', 'w', newline='') as output_file:
reader = csv.reader(input_file)
next(reader, None)
writer = csv.writer(output_file)
for row in reader:
floatParse = float(row[1]) + 1
closestInteger = int(round(floatParse))
stringConvert = str(closestInteger)
row[1] = stringConvert
writer.writerow(row)
I have a csv file with the following columns:
id,name,age,sex
Followed by a lot of values for the above columns.
I am trying to read the column names alone and put them inside a list.
I am using Dictreader and this gives out the correct details:
with open('details.csv') as csvfile:
i=["name","age","sex"]
re=csv.DictReader(csvfile)
for row in re:
for x in i:
print row[x]
But what I want to do is, I need the list of columns, ("i" in the above case)to be automatically parsed with the input csv than hardcoding them inside a list.
with open('details.csv') as csvfile:
rows=iter(csv.reader(csvfile)).next()
header=rows[1:]
re=csv.DictReader(csvfile)
for row in re:
print row
for x in header:
print row[x]
This gives out an error
Keyerrror:'name'
in the line print row[x]. Where am I going wrong? Is it possible to fetch the column names using Dictreader?
Though you already have an accepted answer, I figured I'd add this for anyone else interested in a different solution-
Python's DictReader object in the CSV module (as of Python 2.6 and above) has a public attribute called fieldnames.
https://docs.python.org/3.4/library/csv.html#csv.csvreader.fieldnames
An implementation could be as follows:
import csv
with open('C:/mypath/to/csvfile.csv', 'r') as f:
d_reader = csv.DictReader(f)
#get fieldnames from DictReader object and store in list
headers = d_reader.fieldnames
for line in d_reader:
#print value in MyCol1 for each row
print(line['MyCol1'])
In the above, d_reader.fieldnames returns a list of your headers (assuming the headers are in the top row).
Which allows...
>>> print(headers)
['MyCol1', 'MyCol2', 'MyCol3']
If your headers are in, say the 2nd row (with the very top row being row 1), you could do as follows:
import csv
with open('C:/mypath/to/csvfile.csv', 'r') as f:
#you can eat the first line before creating DictReader.
#if no "fieldnames" param is passed into
#DictReader object upon creation, DictReader
#will read the upper-most line as the headers
f.readline()
d_reader = csv.DictReader(f)
headers = d_reader.fieldnames
for line in d_reader:
#print value in MyCol1 for each row
print(line['MyCol1'])
You can read the header by using the next() function which return the next row of the reader’s iterable object as a list. then you can add the content of the file to a list.
import csv
with open("C:/path/to/.filecsv", "rb") as f:
reader = csv.reader(f)
i = reader.next()
rest = list(reader)
Now i has the column's names as a list.
print i
>>>['id', 'name', 'age', 'sex']
Also note that reader.next() does not work in python 3. Instead use the the inbuilt next() to get the first line of the csv immediately after reading like so:
import csv
with open("C:/path/to/.filecsv", "rb") as f:
reader = csv.reader(f)
i = next(reader)
print(i)
>>>['id', 'name', 'age', 'sex']
The csv.DictReader object exposes an attribute called fieldnames, and that is what you'd use. Here's example code, followed by input and corresponding output:
import csv
file = "/path/to/file.csv"
with open(file, mode='r', encoding='utf-8') as f:
reader = csv.DictReader(f, delimiter=',')
for row in reader:
print([col + '=' + row[col] for col in reader.fieldnames])
Input file contents:
col0,col1,col2,col3,col4,col5,col6,col7,col8,col9
00,01,02,03,04,05,06,07,08,09
10,11,12,13,14,15,16,17,18,19
20,21,22,23,24,25,26,27,28,29
30,31,32,33,34,35,36,37,38,39
40,41,42,43,44,45,46,47,48,49
50,51,52,53,54,55,56,57,58,59
60,61,62,63,64,65,66,67,68,69
70,71,72,73,74,75,76,77,78,79
80,81,82,83,84,85,86,87,88,89
90,91,92,93,94,95,96,97,98,99
Output of print statements:
['col0=00', 'col1=01', 'col2=02', 'col3=03', 'col4=04', 'col5=05', 'col6=06', 'col7=07', 'col8=08', 'col9=09']
['col0=10', 'col1=11', 'col2=12', 'col3=13', 'col4=14', 'col5=15', 'col6=16', 'col7=17', 'col8=18', 'col9=19']
['col0=20', 'col1=21', 'col2=22', 'col3=23', 'col4=24', 'col5=25', 'col6=26', 'col7=27', 'col8=28', 'col9=29']
['col0=30', 'col1=31', 'col2=32', 'col3=33', 'col4=34', 'col5=35', 'col6=36', 'col7=37', 'col8=38', 'col9=39']
['col0=40', 'col1=41', 'col2=42', 'col3=43', 'col4=44', 'col5=45', 'col6=46', 'col7=47', 'col8=48', 'col9=49']
['col0=50', 'col1=51', 'col2=52', 'col3=53', 'col4=54', 'col5=55', 'col6=56', 'col7=57', 'col8=58', 'col9=59']
['col0=60', 'col1=61', 'col2=62', 'col3=63', 'col4=64', 'col5=65', 'col6=66', 'col7=67', 'col8=68', 'col9=69']
['col0=70', 'col1=71', 'col2=72', 'col3=73', 'col4=74', 'col5=75', 'col6=76', 'col7=77', 'col8=78', 'col9=79']
['col0=80', 'col1=81', 'col2=82', 'col3=83', 'col4=84', 'col5=85', 'col6=86', 'col7=87', 'col8=88', 'col9=89']
['col0=90', 'col1=91', 'col2=92', 'col3=93', 'col4=94', 'col5=95', 'col6=96', 'col7=97', 'col8=98', 'col9=99']
How about
with open(csv_input_path + file, 'r') as ft:
header = ft.readline() # read only first line; returns string
header_list = header.split(',') # returns list
I am assuming your input file is CSV format.
If using pandas, it takes more time if the file is big size because it loads the entire data as the dataset.
I am just mentioning how to get all the column names from a csv file.
I am using pandas library.
First we read the file.
import pandas as pd
file = pd.read_csv('details.csv')
Then, in order to just get all the column names as a list from input file use:-
columns = list(file.head(0))
Thanking Daniel Jimenez for his perfect solution to fetch column names alone from my csv, I extend his solution to use DictReader so we can iterate over the rows using column names as indexes. Thanks Jimenez.
with open('myfile.csv') as csvfile:
rest = []
with open("myfile.csv", "rb") as f:
reader = csv.reader(f)
i = reader.next()
i=i[1:]
re=csv.DictReader(csvfile)
for row in re:
for x in i:
print row[x]
here is the code to print only the headers or columns of the csv file.
import csv
HEADERS = next(csv.reader(open('filepath.csv')))
print (HEADERS)
Another method with pandas
import pandas as pd
HEADERS = list(pd.read_csv('filepath.csv').head(0))
print (HEADERS)
import pandas as pd
data = pd.read_csv("data.csv")
cols = data.columns
I literally just wanted the first row of my data which are the headers I need and didn't want to iterate over all my data to get them, so I just did this:
with open(data, 'r', newline='') as csvfile:
t = 0
for i in csv.reader(csvfile, delimiter=',', quotechar='|'):
if t > 0:
break
else:
dbh = i
t += 1
Using pandas is also an option.
But instead of loading the full file in memory, you can retrieve only the first chunk of it to get the field names by using iterator.
import pandas as pd
file = pd.read_csv('details.csv'), iterator=True)
column_names_full=file.get_chunk(1)
column_names=[column for column in column_names_full]
print column_names
I have no knowledge of python.
What i want to be able to do is create a script that will edit a CSV file so that it will wrap every field in column 3 around quotes. I haven't been able to find much help, is this quick and easy to do? Thanks.
column1,column2,column3
1111111,2222222,333333
This is a fairly crude solution, very specific to your request (assuming your source file is called "csvfile.csv" and is in C:\Temp).
import csv
newrow = []
csvFileRead = open('c:/temp/csvfile.csv', 'rb')
csvFileNew = open('c:/temp/csvfilenew.csv', 'wb')
# Open the CSV
csvReader = csv.reader(csvFileRead, delimiter = ',')
# Append the rows to variable newrow
for row in csvReader:
newrow.append(row)
# Add quotes around the third list item
for row in newrow:
row[2] = "'"+str(row[2])+"'"
csvFileRead.close()
# Create a new CSV file
csvWriter = csv.writer(csvFileNew, delimiter = ',')
# Append the csv with rows from newrow variable
for row in newrow:
csvWriter.writerow(row)
csvFileNew.close()
There are MUCH more elegant ways of doing what you want, but I've tried to break it down into basic chunks to show how each bit works.
I would start by looking at the csv module.
import csv
filename = 'file.csv'
with open(filename, 'wb') as f:
reader = csv.reader(f)
for row in reader:
row[2] = "'%s'" % row[2]
And then write it back in the csv file.
I need a way to get a specific item(field) of a CSV. Say I have a CSV with 100 rows and 2 columns (comma seperated). First column emails, second column passwords. For example I want to get the password of the email in row 38. So I need only the item from 2nd column row 38...
Say I have a csv file:
aaaaa#aaa.com,bbbbb
ccccc#ccc.com,ddddd
How can I get only 'ddddd' for example?
I'm new to the language and tried some stuff with the csv module, but I don't get it...
import csv
mycsv = csv.reader(open(myfilepath))
for row in mycsv:
text = row[1]
Following the comments to the SO question here, a best, more robust code would be:
import csv
with open(myfilepath, 'rb') as f:
mycsv = csv.reader(f)
for row in mycsv:
text = row[1]
............
Update: If what the OP actually wants is the last string in the last row of the csv file, there are several aproaches that not necesarily needs csv. For example,
fulltxt = open(mifilepath, 'rb').read()
laststring = fulltxt.split(',')[-1]
This is not good for very big files because you load the complete text in memory but could be ok for small files. Note that laststring could include a newline character so strip it before use.
And finally if what the OP wants is the second string in line n (for n=2):
Update 2: This is now the same code than the one in the answer from J.F.Sebastian. (The credit is for him):
import csv
line_number = 2
with open(myfilepath, 'rb') as f:
mycsv = csv.reader(f)
mycsv = list(mycsv)
text = mycsv[line_number][1]
............
#!/usr/bin/env python
"""Print a field specified by row, column numbers from given csv file.
USAGE:
%prog csv_filename row_number column_number
"""
import csv
import sys
filename = sys.argv[1]
row_number, column_number = [int(arg, 10)-1 for arg in sys.argv[2:])]
with open(filename, 'rb') as f:
rows = list(csv.reader(f))
print rows[row_number][column_number]
Example
$ python print-csv-field.py input.csv 2 2
ddddd
Note: list(csv.reader(f)) loads the whole file in memory. To avoid that you could use itertools:
import itertools
# ...
with open(filename, 'rb') as f:
row = next(itertools.islice(csv.reader(f), row_number, row_number+1))
print row[column_number]
import csv
def read_cell(x, y):
with open('file.csv', 'r') as f:
reader = csv.reader(f)
y_count = 0
for n in reader:
if y_count == y:
cell = n[x]
return cell
y_count += 1
print (read_cell(4, 8))
This example prints cell 4, 8 in Python 3.
There is an interesting point you need to catch about csv.reader() object. The csv.reader object is not list type, and not subscriptable.
This works:
for r in csv.reader(file_obj): # file not closed
print r
This does not:
r = csv.reader(file_obj)
print r[0]
So, you first have to convert to list type in order to make the above code work.
r = list( csv.reader(file_obj) )
print r[0]
Finaly I got it!!!
import csv
def select_index(index):
csv_file = open('oscar_age_female.csv', 'r')
csv_reader = csv.DictReader(csv_file)
for line in csv_reader:
l = line['Index']
if l == index:
print(line[' "Name"'])
select_index('11')
"Bette Davis"
Following may be be what you are looking for:
import pandas as pd
df = pd.read_csv("table.csv")
print(df["Password"][row_number])
#where row_number is 38 maybe
import csv
inf = csv.reader(open('yourfile.csv','r'))
for row in inf:
print row[1]
I have a large csv file in which some rows are entirely blank. How do I use Python to delete all blank rows from the csv?
After all your suggestions, this is what I have so far
import csv
# open input csv for reading
inputCSV = open(r'C:\input.csv', 'rb')
# create output csv for writing
outputCSV = open(r'C:\OUTPUT.csv', 'wb')
# prepare output csv for appending
appendCSV = open(r'C:\OUTPUT.csv', 'ab')
# create reader object
cr = csv.reader(inputCSV, dialect = 'excel')
# create writer object
cw = csv.writer(outputCSV, dialect = 'excel')
# create writer object for append
ca = csv.writer(appendCSV, dialect = 'excel')
# add pre-defined fields
cw.writerow(['FIELD1_','FIELD2_','FIELD3_','FIELD4_'])
# delete existing field names in input CSV
# ???????????????????????????
# loop through input csv, check for blanks, and write all changes to append csv
for row in cr:
if row or any(row) or any(field.strip() for field in row):
ca.writerow(row)
# close files
inputCSV.close()
outputCSV.close()
appendCSV.close()
Is this ok or is there a better way to do this?
Use the csv module:
import csv
...
with open(in_fnam, newline='') as in_file:
with open(out_fnam, 'w', newline='') as out_file:
writer = csv.writer(out_file)
for row in csv.reader(in_file):
if row:
writer.writerow(row)
If you also need to remove rows where all of the fields are empty, change the if row: line to:
if any(row):
And if you also want to treat fields that consist of only whitespace as empty you can replace it with:
if any(field.strip() for field in row):
Note that in Python 2.x and earlier, the csv module expected binary files, and so you'd need to open your files with e 'b' flag. In 3.x, doing this will result in an error.
Surprised that nobody here mentioned pandas. Here is a possible solution.
import pandas as pd
df = pd.read_csv('input.csv')
df.to_csv('output.csv', index=False)
Delete empty row from .csv file using python
import csv
...
with open('demo004.csv') as input, open('demo005.csv', 'w', newline='') as output:
writer = csv.writer(output)
for row in csv.reader(input):
if any(field.strip() for field in row):
writer.writerow(row)
Thankyou
You have to open a second file, write all non blank lines to it, delete the original file and rename the second file to the original name.
EDIT: a real blank line will be like '\n':
for line in f1.readlines():
if line.strip() == '':
continue
f2.write(line)
a line with all blank fields would look like ',,,,,\n'. If you consider this a blank line:
for line in f1.readlines():
if ''.join(line.split(',')).strip() == '':
continue
f2.write(line)
openning, closing, deleting and renaming the files is left as an exercise for you. (hint: import os, help(open), help(os.rename), help(os.unlink))
EDIT2: Laurence Gonsalves brought to my attention that a valid csv file could have blank lines embedded in quoted csv fields, like 1, 'this\n\nis tricky',123.45. In this case the csv module will take care of that for you. I'm sorry Laurence, your answer deserved to be accepted. The csv module will also address the concerns about a line like "","",""\n.
Doing it with pandas is very simple. Open your csv file with pandas:
import pandas as pd
df = pd.read_csv("example.csv")
#checking the number of empty rows in th csv file
print (df.isnull().sum())
#Droping the empty rows
modifiedDF = df.dropna()
#Saving it to the csv file
modifiedDF.to_csv('modifiedExample.csv',index=False)
python code for remove blank line from csv file without create another file.
def ReadWriteconfig_file(file):
try:
file_object = open(file, 'r')
lines = csv.reader(file_object, delimiter=',', quotechar='"')
flag = 0
data=[]
for line in lines:
if line == []:
flag =1
continue
else:
data.append(line)
file_object.close()
if flag ==1: #if blank line is present in file
file_object = open(file, 'w')
for line in data:
str1 = ','.join(line)
file_object.write(str1+"\n")
file_object.close()
except Exception,e:
print e
Here is a solution using pandas that removes blank rows.
import pandas as pd
df = pd.read_csv('input.csv')
df.dropna(axis=0, how='all',inplace=True)
df.to_csv('output.csv', index=False)
I need to do this but not have a blank row written at the end of the CSV file like this code unfortunately does (which is also what Excel does if you Save-> .csv). My (even simpler) code using the CSV module does this too:
import csv
input = open("M51_csv_proc.csv", 'rb')
output = open("dumpFile.csv", 'wb')
writer = csv.writer(output)
for row in csv.reader(input):
writer.writerow(row)
input.close()
output.close()
M51_csv_proc.csv has exactly 125 rows; the program always outputs 126 rows, the last one being blank.
I've been through all these threads any nothing seems to change this behaviour.
In this script all the CR / CRLF are removed from a CSV file then has lines like this:
"My name";mail#mail.com;"This is a comment.
Thanks!"
Execute the script https://github.com/eoconsulting/lr2excelcsv/blob/master/lr2excelcsv.py
Result (in Excel CSV format):
"My name",mail#mail.com,"This is a comment. Thanks!"
Replace the PATH_TO_YOUR_CSV with your
import pandas as pd
df = pd.read_csv('PATH_TO_YOUR_CSV')
new_df = df.dropna()
df.dropna().to_csv('output.csv', index=False)
or in-line:
import pandas as pd
pd.read_csv('data.csv').dropna().to_csv('output.csv', index=False)
I had the same, problem.
I converted the .csv file to a dataframe and after that I converted the dataframe back to the .csv file.
The initial .csv file with the blank lines was the 'csv_file_logger2.csv' .
So, i do the following process
import csv
import pandas as pd
df=pd.read_csv('csv_file_logger2.csv')
df.to_csv('out2.csv',index = False)