Using DictReader and given a file that contains data like so:
First ,Last,fruit,fruit,fruit,fruit,fruit,fruit
Carl,Yung,apple,watermelon,,,,
Louis,Pasteur,banana,grape,mango,,,
Marie,Curie,watermelon,apple,banana,,,
How do I assign any non-empty "fruit" fields to a list so that when the following code executes, row['fruit'] contains that list.
with open(csv_file) as csvfile:
reader = csv.DictReader(csvfile)
for row in reader:
print(row['First'],row['Last'],row['fruit'], sep='--->')
If fieldnames is omitted, the values in the first row will be used as the fieldnames. But you may specify it explicitly. If a row has more fields than fieldnames, the remaining data is put in a list and stored with the fieldname specified by restkey (which defaults to None).
import csv
with open("myfile.csv") as f:
reader = csv.DictReader(f, fieldnames=("First", "Last"), restkey="fruit")
for row in reader:
print(row)
Related
I am trying to write a simple program that should give the following output when it reads csv file which contains several email ids.
email_id = ['emailid1#xyz.com','emailid2#xyz.com','emailid3#xyz.com'] #required format
but the problem is the output I got is like this following:
[['emailid1#xyz.com']]
[['emailid1#xyz.com'], ['emailid2#xyz.com']]
[['emailid1#xyz.com'], ['emailid2#xyz.com'], ['emailid3#xyz.com']] #getting this wrong format
here is my piece of code that I have written: Kindly suggest me the correction in the following piece of code which would give me the required format. Thanks in advance.
import csv
email_id = []
with open('contacts1.csv', 'r') as file:
reader = csv.reader(file, delimiter = ',')
for row in reader:
email_id.append(row)
print(email_id)
NB.: Note my csv contains only one column that has email ids and has no header. I also tried the email_id.extend(row) but It did not work also.
You need to move your print outside the loop:
with open('contacts1.csv', 'r') as file:
reader = csv.reader(file, delimiter = ',')
for row in reader:
email_id.append(row)
print(sum(email_id, []))
The loop can also be like this (if you only need one column from the csv):
for row in reader:
email_id.append(row[0])
print(email_id)
import csv
email = 'someone#somemail.com'
password = 'password123'
with open('test.csv', 'a', newline='') as accts:
b = csv.writer(accts, delimiter=',')
b.writerow(email)
b.writerow(password)
I'm trying to append to a csv file with the format email:password on the same row, but everytime I run the program it creates a new row for each letter and the password is written under the email. What am I doing wrong?
Output:
s,o,m,e,o,n,e,#,s,o,m,e,m,a,i,l,.,c,o,m
p,a,s,s,w,o,r,d,1,2,3
Desired output:
someone#somemail.com,password123
A string looks like a list of individual characters, and writerow expects a list of the column values, so you end up with columns of individual characters.
Instead, use a list of the column values:
b.writerow([email,password])
I'm trying to create a list of lists from a csv file.
Row 1 of CSV is a line describing the data source
Row 2 of CSV is the header
Row 3 of CSV is where the data starts
There are two ways I can go about it but I don't know why they're different.
First is the using list() and for some reason the result of this ignores row 1 and row 2 of the CSV.
data = []
with open(datafile,'rb') as f:
for line in f:
data = list(csv.reader(f, delimiter = ','))
return (name, data)
Whereas if I use .append(), I'd have to use .next() to skip row 2
data = []
with open(datafile,'rb') as f:
file = csv.reader(f, delimiter = ',')
next(file)
for line in file:
data.append(line)
return (name, data)
Why does list() ignores the row with all the header whereas append() doesn't?
Actually, this is not related to python's list() or append(), it is related to the logic you have used in the first snippet.
The program is not skipping the header, it is replacing it.
For every line in the loop, you are assigning a new value to data. So it is a new list , as it overwrites everything that was there previously.
Correct code :
data = []
with open(datafile,'rb') as f:
next(f)
for line in f:
data.extend(line.split(","))
return (name, data)
This will just extend the existing list with a new list that is passed as an argument, and there is no problem with 2nd snippet.
I have this in csv file:
Titre,a,b,c,d,e
01,jean,paul,,
01,,,jack,
02,jeanne,jack,,
02,,,jean
and i want :
Titre,a,b,c,d,e
01,jean,paul,jack,
02,jeanne,jack,,jean
can you help me ?
In general, a good approach is to read the csv file and iterate through the rows using Python's CSV module.
CSV will create an iterator that will let you loop through your file like this:
import csv
with open('your filename.csv', 'r') as infile:
reader = csv.reader(infile)
for line in reader:
for value in line:
# Do your thing
You're going to need to construct a new data set that has different properties. The requirements you described:
Ignore any empty cells
Any time you encounter a row that has a new index number, add a new row to your new data set
Any time you encounter a row that has an index number you've seen before, add it to the row that you already created (except for that index number value itself)
I'm not writing that part of the code for you because you need to learn and grow. It's a good task for a beginner.
Once you've constructed that data set, it will look like this:
example_processed_data = [["Titre","a","b","c","d","e"],
["01","jean","paul","jack"],
["02","jeanne","jack","","jean"]]
You can then create a CSV writer, and create your outfile by iterating over that data, similarly to how you iterated over the infile:
with open('outfile.csv', 'w') as outfile:
writer = csv.writer(outfile)
for line in example_processed_data:
writer.writerow(line)
print("Done! Wrote", len(example_processed_data), "lines to outfile.csv.")
I am trying read a CSV file into python 3 using unicodecsv library. Code follows :
with open('filename.csv', 'rb') as f:
reader = unicodecsv.DictReader(f)
Student_Data = list(reader)
But the order of the columns in the CSV file is not retained when I output any element from the Student_Data. The output contains any random order of the columns. Is there anything wrong with the code? How do I fix this?
As stated in csv.DictReader documentation, the DictReader object behaves like a dict - so it is not ordered.
You can obtain the list of the fieldnames with:
reader.fieldnames
But if you only want to obtain a list of the field values, in original order, you can just use a normal reader:
with open('filename.csv', 'rb') as f:
reader = unicodecsv.reader(f)
for row in reader:
Student_Data = row