Row count in a csv file
Question:
I am probably making a stupid mistake, but I can’t find where it is. I want to count the number of lines in my csv file. I wrote this, and obviously isn’t working: I have row_count = 0 while it should be 400. Cheers.
f = open(adresse,"r")
reader = csv.reader(f,delimiter = ",")
data = [l for l in reader]
row_count = sum(1 for row in reader)
print row_count
Answers:
with open(adresse,"r") as f:
reader = csv.reader(f,delimiter = ",")
data = list(reader)
row_count = len(data)
You are trying to read the file twice, when the file pointer has already reached the end of file after saving the data list.
First you have to open the file with open
input_file = open("nameOfFile.csv","r+")
Then use the csv.reader for open the csv
reader_file = csv.reader(input_file)
At the last, you can take the number of row with the instruction ‘len’
value = len(list(reader_file))
The total code is this:
input_file = open("nameOfFile.csv","r+")
reader_file = csv.reader(input_file)
value = len(list(reader_file))
Remember that if you want to reuse the csv file, you have to make a input_file.fseek(0), because when you use a list for the reader_file, it reads all file, and the pointer in the file change its position
If you are working with python3 and have pandas library installed you can go with
import pandas as pd
results = pd.read_csv('f.csv')
print(len(results))
# with built in libraries
opened_file = open('f.csv')
from csv import reader
read_file = reader(opened_file)
apps_data = list(read_file)
rowcount = len(apps_data) #which incudes header row
print("Total rows incuding header: " + str(rowcount))
Simply Open the csv file in Notepad++. It shows the total row count in a jiffy. 🙂
Or
in cmd prompt , Provide file path and key in the command
find c v “some meaningless string” Filename.csv
I would consider using a generator. It would do the job and keeps you safe from MemoryError of any kind
def generator_count_file_rows(input_file):
for row in open(input_file,'r'):
yield row
And then
for row in generator_count_file_rows('very_large_set.csv'):
count+=1
The important stuff is hidden in comments section of solution which is marked correct.
Re-sharing ErdÅ‘s-Bacon’s solution here for better visibility.
Why ?
Because: It saves lot of memory without having to create list.
So I think it is better do this way
def read_raw_csv(file_name):
with open(file_name, 'r') as file:
csvreader = csv.reader(file)
# count number of rows
entry_count = sum(1 for row in csvreader)
print(entry_count-1) # -1 is for discarding header row.
Checkout this link for more info
I am probably making a stupid mistake, but I can’t find where it is. I want to count the number of lines in my csv file. I wrote this, and obviously isn’t working: I have row_count = 0 while it should be 400. Cheers.
f = open(adresse,"r")
reader = csv.reader(f,delimiter = ",")
data = [l for l in reader]
row_count = sum(1 for row in reader)
print row_count
with open(adresse,"r") as f:
reader = csv.reader(f,delimiter = ",")
data = list(reader)
row_count = len(data)
You are trying to read the file twice, when the file pointer has already reached the end of file after saving the data list.
First you have to open the file with open
input_file = open("nameOfFile.csv","r+")
Then use the csv.reader for open the csv
reader_file = csv.reader(input_file)
At the last, you can take the number of row with the instruction ‘len’
value = len(list(reader_file))
The total code is this:
input_file = open("nameOfFile.csv","r+")
reader_file = csv.reader(input_file)
value = len(list(reader_file))
Remember that if you want to reuse the csv file, you have to make a input_file.fseek(0), because when you use a list for the reader_file, it reads all file, and the pointer in the file change its position
If you are working with python3 and have pandas library installed you can go with
import pandas as pd
results = pd.read_csv('f.csv')
print(len(results))
# with built in libraries
opened_file = open('f.csv')
from csv import reader
read_file = reader(opened_file)
apps_data = list(read_file)
rowcount = len(apps_data) #which incudes header row
print("Total rows incuding header: " + str(rowcount))
Simply Open the csv file in Notepad++. It shows the total row count in a jiffy. 🙂
Or
in cmd prompt , Provide file path and key in the command
find c v “some meaningless string” Filename.csv
I would consider using a generator. It would do the job and keeps you safe from MemoryError of any kind
def generator_count_file_rows(input_file):
for row in open(input_file,'r'):
yield row
And then
for row in generator_count_file_rows('very_large_set.csv'):
count+=1
The important stuff is hidden in comments section of solution which is marked correct.
Re-sharing ErdÅ‘s-Bacon’s solution here for better visibility.
Why ?
Because: It saves lot of memory without having to create list.
So I think it is better do this way
def read_raw_csv(file_name):
with open(file_name, 'r') as file:
csvreader = csv.reader(file)
# count number of rows
entry_count = sum(1 for row in csvreader)
print(entry_count-1) # -1 is for discarding header row.
Checkout this link for more info