How to save string and array in the same row into csv by using python?

Question

I have a vector, it is np.array([[1,2,3]]).

I want to save the vector and the name of the vector in the same row.

For example

Vector1 1 2 3

Vector2 4 5 6

Vector3 7 8 9

Then, I have ever tried like this

import csv
import numpy as np
a=np.array([[1,2,3]])
b='Vector1'
c=[b,a]
with open ('testfile.csv','ab') as fxx:
        w=csv.writer(fxx)
        for row in c:
            w.writerow(row)

the result is

then I also have tried this

import csv
import numpy as np
a=np.array([[1,2,3]])
b='Vector1'
c=np.append(b,a)
with open ('testfile3.csv','ab') as fxx:
        w=csv.writer(fxx)
        for row in c:
            w.writerow(row)

And then the result is

But the result what I want is

Goran · Accepted Answer · 2018-06-18 11:36:21Z

1

import csv
import numpy as np
a=np.array([[1,2,3]])
b='Vector1'
c=np.append(b,a)
print(c)
with open ('testfile3.csv','a') as fxx:
        w=csv.writer(fxx)
        w.writerow(c)

answered Jun 18, 2018 at 11:36

Goran

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Comments

bruno desthuilliers · Accepted Answer · 2018-06-18 11:42:08Z

writerow() expects a sequence where each element will fill a column, ie

`writer.writerow(["foo", 42, "bar")

will result in (quoting and delimiter depending on your writer params):

"foo",42,"bar"

In your code you create a list c as:

c=['Vector1', [[1, 2, 3]]]

ie your first element is a string and the second a list of one element which is another list.

then iterate over this list to pass each of it's elements to your writer, so basically what you're doing is:

writer.writerow("Vector1")
writer.writerow([[1, 2, 3]])

For the first line, since strings are sequences, it will fill one column per character resulting in (quoting and delim depending on your writer config) :

"V","e","c","t","o","r","1"

and for the second, since you pass a list of one element, it will fill one single column with the string representation of the single element in the list:

"[1, 2, 3]"

If what you want is

"Vector1",1,2,3

then the obvious solution is to pass the correct sequence to writerow:

writer.writerow(["Vector1", 1, 2, 3])

Now you just have to change your code to correctly produce this sequence...

Nihal · Accepted Answer · 2018-06-18 12:22:23Z

0

import pandas as pd
a = [[1, 2, 3]]
b = 'Vector1'
a[0].append(b)
print(a)
df = pd.DataFrame(a)
print(df)
df.to_csv('data.csv')

output:

 0  1  2        3
0  1  2  3  Vector1

edited Jun 18, 2018 at 12:22

answered Jun 18, 2018 at 11:36

Nihal

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