Writing data to a text file in Python

Question

I am trying to write mean,var,std to a .txt file but I am getting an error.

import csv
mean = 50.00001075309713
var = 4.120598729047652
std = 2.0299257939756448

with open('Radius.txt', 'w+') as f: 
    writer = csv.writer(f)
    print("Mean =",mean)
    print("var =",var)
    print("std =",std)
    writer.writerow(mean)
    writer.writerow(var)
    writer.writerow(std)

The error is

in <module>
    writer.writerow(mean)

Error: iterable expected, not float

The expected output is

mean = 50.00001075309713
var = 4.120598729047652
std = 2.0299257939756448

We can see from the docs that: "A row must be an iterable of strings or numbers". A float is not iterable, so you need to wrap it in an iterable container like a list or a tuple. — 0x5453
– 0x5453, Commented Sep 7, 2022 at 15:05
Does this answer your question? How to fix "Error: iterable expected, not int" when writing to a CSV file? — TheFungusAmongUs
– TheFungusAmongUs, Commented Sep 7, 2022 at 15:06
Do you need the csv format or are you happy with a txt file containing the 3 lines from your expected output? — MagnusO_O
– MagnusO_O, Commented Sep 7, 2022 at 15:22
CSV format is not mandatory. The expected output in a txt file will do. — user19862793
– user19862793, Commented Sep 7, 2022 at 15:23

Crapicus · Accepted Answer · 2022-09-07 15:24:44Z

2

Change:

writer.writerow(mean)
writer.writerow(var)
writer.writerow(std)

to:

writer.writerow((mean, var, std))

The requirement for an iterable means whatever you pass to writerow must be something which can be looped through. The fix here is to put your values into a tuple, the inner bracketed values. It works because tuples can be looped through. 👍

To write the values as a single line with variable prefixes (OP's comment) use:

writer.writerow((f'{mean = }  {var = }  {std = }', ))

edited Sep 7, 2022 at 15:24

answered Sep 7, 2022 at 15:04

Crapicus

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6 Comments

user19862793 Over a year ago

I have now included the expected output. How can writer.writerow((mean, var, std)) be modified?

Crapicus Over a year ago

Modify any of the values mean, var and std by assigning their values: var = 123... Each new call to writerow would create a new tuple from the modified values. A tuple itself cannot be modified, but that doesn't affect our use case here because we are creating a new tuple purely for writerow. The tuple doesn't exist after that but your values still do in their respective named variables mean, var and std.

user19862793 Over a year ago

I mean how do I save values in this format: mean = 50.00001075309713 var = 4.120598729047652 std = 2.0299257939756448 as shown in the expected output.

Crapicus Over a year ago

see updated reply

user19862793 Over a year ago

With the updated reply, it is saving as

m,e,a,n, ,=, ,5,0,.,0,0,0,0,1,0,7,5,3,0,9,7,1,3, ,v,a,r, ,=, ,4,.,1,2,0,5,9,8,7,2,9,0,4,7,6,5,2, ,s,t,d, ,=, ,2,.,0,2,9,9,2,5,7,9,3,9,7,5,6,4,4,8

which is not the expected output.

|

MagnusO_O · Accepted Answer · 2022-09-07 15:30:41Z

2

Based on the clarification from the comments a way without using csv but just a txt file:

mean = 50.00001075309713
var = 4.120598729047652
std = 2.0299257939756448

with open('Radius.txt', 'w+') as f: 
    f.write(f"mean = {str(mean)}\n")
    f.write(f"var = {str(var)}\n")
    f.write(f"std = {str(std)}\n")

answered Sep 7, 2022 at 15:30

MagnusO_O

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