How to add numbers in Text file with Strings [duplicate] - python-3.x

Question

This question already has an answer here:
How to perform addition in text file bypassing strings
(1 answer)
Closed 4 years ago.
import csv
csv_file = 'Annual Budget.csv'
txt_file = 'annual_budget.txt'
with open(txt_file, 'w') as my_output_file:
with open(csv_file, 'r') as my_input_file:
reader = csv.reader(my_input_file)
for row in reader:
my_output_file.write(" ".join(row)+'\n')
data = []
with open(r'annual_budget.txt', 'r') as f:
reader = csv.reader(f)
header = next(reader)
for line in reader:
rowdata = map(float, line)
data.extend(rowdata)
print(sum(data)/len(data))
Trying to add the numbers in a text file with strings but error is continually thrown.
Output:
data.extend(rowdata)
ValueError: could not convert string to float:
Data Set: [1]: https://i.stack.imgur.com/xON30.png

Answer 1

TLDR: You're treating space delimited text as csv which is not parsing correctly by the csv module.
At the time I worked this problem out for you, you had not provided origional csv data, so for this problem I assumed your csv file contained the following data, based on your screenshot of the txt file.
Annual Budget,Q2,Q4
100,450,20
600,765,50
500,380,79
800,480,455
1100,65,4320
Now, about the code.
You're defining data = [] in a place where it is not only
not used, but also causing it to be reset to an empty
list with every loop through the file you're converting.
If we add a print statement directly under it we get this for output:
showing added print statement:
with open(txt_file, 'w') as my_output_file:
with open(csv_file, 'r') as my_input_file:
reader = csv.reader(my_input_file)
for row in reader:
my_output_file.write(" ".join(row)+'\n')
data = []
print(data)
Output:
[]
[]
[]
[]
[]
[]
Moving data = [] to the top of the file prevents that.
Now with the second with statement and loops you're treating the txt file you just created as a csv file. csv data is comma delimited not space delimited. The csv reader isn't parsing the row correctly. if we add a print loop to check what is coming out of the map function we can see it's not doing what you're expecting it to, which is convert it to a list of floats.
Relevent code:
for line in reader:
rowdata = map(float, line)
for element in rowdata:
print(element)
output:
Traceback (most recent call last):
File "test.py", line 17, in <module>
for element in rowdata:
ValueError: could not convert string to float: '100 450 20'
There are multiple ways to solve the problem, but I think the best is to simply skip the whole first loop where you convert it to a space delimited file. Doing so we just depend on the csv module to do it's job.
example code:
import csv
data = []
with open('Annual Budget.csv', 'r') as f:
reader = csv.reader(f) # Gets the reader
header = next(reader) # advance the reader past the header.
for line in reader:
rowdata = map(float, line)
for element in rowdata:
print(element)
Output:
100.0
450.0
20.0
600.0
765.0
50.0
500.0
380.0
79.0
800.0
480.0
455.0
1100.0
65.0
4320.0
Now we'll add your last couple lines of code back in and remove the test code:
import csv
data = []
with open('Annual Budget.csv', 'r') as f:
reader = csv.reader(f) # Gets the reader
header = next(reader) # advance the reader past the header.
for line in reader:
rowdata = map(float, line)
data.extend(rowdata)
print(sum(data)/len(data))
Which now outputs:
677.6