Adding values from a CSV file

Adding values from a CSV file

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I am beginning to learn python and am struggling with Syntax.

I have a simple CSV file that looks like this


I want to look for the highest and lowest value in all the data in the csv file except in the first value of each row.

So effectively the answer here would be


because the data that is looked at is as follows (it ignored the first value of each row)


I would like my code to work for ANY row length.

I really have to admit I'm struggling but here's what I've tried. I usually program PHP so this is all new to me. I have been working on this simple task for a day and can't fathom it out. I think I'm getting confused with terminology 'lists' for example.

import numpy

test_data_file = open ("Anaconda3JamesData/james_test_3.csv","r")
test_data_list = test_data_file.readlines()

for record in test_data_list:
    all_values = record.split(',')
    maxvalue = np.max(numpy.asfarray(all_values[1:])

print (maxvalue)

With the test data (the CSV file shown at the very top of this question) I would expect the answer to be


If you're using numpy, you can read your csv file as a numpy.ndarray using numpy.genfromtxt() and then use the array's .max() and .min() methods

import numpy
array = numpy.genfromtxt('Anaconda3JamesData/james_test_3.csv', delimiter=',')
array[:, 1:].max()
array[:, 1:].min()

The [:, 1:] part is using numpy's array indexing. It's saying take all the rows (the first [:, part), and for each row take all but the first column (the 1:] part) . This doesn't work with Python's built in lists.

Python: How to append a new row to an existing csv file , to the writer: // Our example data List<List<String>> rows = Arrays. Here are the steps to load data from CSV file in Java without using any third party library : Open CSV file using FileReader object; Create BufferedReader from FileReader; Read file line by line using readLine() method; Split each line on comma to get an array of attributes using String.split() method

You're overwriting maxvalue each time through the loop, so you're just getting the max value from the last line, not the whole file. You need to compare with the previous maximum.

maxvalue = None
for record in test_data_list:
    all_values = record.split(',')
    if maxvalue is None:
        maxvalue = np.max(numpy.asfarray(all_values[1:])
        maxvalue = max(maxvalue, np.max(numpy.asfarray(all_values[1:]))

Reading and Writing CSVs in Java, hi..suppose i have a .csv file named csvfile.csv.And it has the values as follows: 23 45. 69 84. 48 78. 12 34. so it has two colums.Now wat i need to do is to add  Open table to which the data is loaded. Review the data, click Apply button. MySQL workbench will display a dialog “Apply SQL Script to Database”, click Apply button to insert data into the table. We have shown you how to import CSV into MySQL table using LOAD DATA LOCAL and using MySQL Workbench.

You do not need the power of numpy for this problem. A simple CSV reader is good enough:

with open("Anaconda3JamesData/james_test_3.csv") as infile:
    r = csv.reader(infile)
    rows = [list(map(float, line))[1:] for line in r]
max(map(max, rows))
# 5647.0
min(map(min, rows))
# 0.35

How to Read a CSV in MATLAB, Add a column with same values to an existing CSV file. Open 'input.csv' file in read mode and create csv.reader object for this csv file. Open 'output.csv' file in write mode and create csv.writer object for this csv file. Using reader object, read the 'input.csv' file line by line. Close both input. Simply close the CSV file and/or any other application that has access to the CSV file, go to the previous screen and click the “Next” button again to fix this. Step 3: Preview the data If your file has loaded successfully, a new window will appear containing a preview of your file, as shown in the following figure:

I think using numpy is unneeded for this task. First of all, this:

test_data_file = open ("Anaconda3JamesData/james_test_3.csv","r")
test_data_list = test_data_file.readlines()

for record in test_data_list:

can be simplified into this:

with open("Anaconda3JamesData/james_test_3.csv","r") as test_data_file:
    for record in test_data_file:

We can use a list comprehension to read in all of the values:

with open("Anaconda3JamesData/james_test_3.csv","r") as test_data_file:
    values = [float(val) for line in test_data_file for val in line.split(",")[1:]]

values now contains all relevant numbers, so we can just do:

highest_value = max(values)
lowest_value = min(values)

How to append data or values to an existing .csv file??, Open our csv file in append mode and create a file object. Pass this file object to the csv. writer(), we can get a writer class object. This writer object has a function writerow() , pass the list to it and it will add list's contents as a new row in the associated csv file. Working with csv files in Python. with open(filename, 'r') as csvfile: csvreader = csv.reader(csvfile) Here, we first open the CSV file in READ mode. The file object is named as fields = csvreader is an iterable object. Hence, .next() method returns the current row and advances

Here's a pandas solution that can give the desired results:

import pandas as pd
df = pd.read_csv('test1.csv', header=None)
# df:
#    0     1   2      3   4     5   6   7    8    9    10
# 0  0.01  10  20   0.35  40    50  60  70   80   90  100
# 1  2.00  22  32  42.00  52    62  72  82   92  102  112
# 2  3.00  33  43  53.00  63  5647  83  93  103  113  123

df = df.iloc[:, 1:] 
print("Highest value: {}".format(df.values.max()))
print("Lowest value: {}".format(df.values.min()))
Highest value: 5647.0
Lowest value: 0.35

Python: Add a column to an existing CSV file –, Euphoria[edit]. --- Read CSV file and add columns headed with 'SUM' --- with trace -- trace(0) In this article, we will discuss how to append a row to an existing csv file using csv module’s reader / writer & DictReader / DictWriter classes. Suppose we have a CSV file students.csv, whose contents are, Id,Name,Course,City,Session 21,Mark,Python,London,Morning 22,John,Python,Tokyo,Evening 23,Sam,Python,Paris,Morning

CSV data manipulation, I have one downloaded csv file. in that we need to add client number in After these while write to csv. i'm getting only 'A' column values not  A CSV (Comma Separated Values) format is one of the most simple and common ways to store tabular data. To represent a CSV file, it must be saved with the .csv file extension. Let's take an example: If you open the above CSV file using a text editor such as sublime text, you will see: SN, Name, City 1, Michael, New Jersey 2, Jack, California

Adding string to a particular column in csv file - Build, CSV (Comma Separated Values) files are one of the most used forms of data storage. This is Suppose we want to add a few lines to the “beneficairy.csv” file. Though we’re reading the data from CSV files with Column headers, we can still have our own column names. We can achieve the same by adding a parameter called names in read_csv() as. df_csv = pd.read_csv('csv_example', names=['a', 'b', 'c']) The resultant DataFrame shall look like

Interacting with CSV files using Python, Open the CSV file created in step 3 in Excel. Add any necessary formulas or make any changes. Export the report in Data Interchange Format (DIF): Note: Only  With the needed spreadsheet open, click the cell where you want to import the data from a.csv or.txt file. On the Data tab, in the Get External Data group, click From Text. Browse for the csv file you want to import, select it and click the Import button (or simply double click the.csv file).