Answers for "how to read a list of numbers in a text file and input it into a list in python"

python write a list to a file line by line

# attempt #1
f = open("Bills.txt", "w")
f.write("n".join(map(lambda x: str(x), bill_List)))
f.close()


# attempt #2
# Open a file in write mode
f = open('Bills.txt', 'w')
for item in bill_List:
f.write("%sn" % item)
# Close opend file
f.close()

# attempt #3

with open('Bills.txt', 'w') as f:
for s in bill_List:
    f.write(s + 'n')

with open('Bills.txt', 'r') as f:
bill_List = [line.rstrip('n') for line in f]

# attempt #4
with open('Bills.txt', 'w') as out_file:
out_file.write('n'.join(
    bill_List))

array storing in file by python

# long arrays can be stored in csv files far more efficiently
import numpy as np
import csv

# uploading arrays in a csv file
arr1 = [i for i in range(500)]
arr2 = [i for i in range(1000)]
arr3 = [i for i in range(2000)]
# you can write('w') or append('a')
with open('record.csv', 'a') as record_append:
    np.savetxt(record_append, np.asarray([arr1]), delimiter=',')
    np.savetxt(record_append, np.asarray([arr2]), delimiter=',')
    np.savetxt(record_append, np.asarray([arr3]), delimiter=',')

# downloading them from the csv file
two_dim_arr = []  # each line of the file is an array element
with open('record.csv', 'r') as record_read:
    reader = csv.reader(record_read)
    for i, each_arr in enumerate(reader):
        two_dim_arr.append([eval(each) for each in each_arr])
        
# printing the arrays in lines
for each_line in two_dim_arr:
  print(each_line)