file_name = 'example'

print(f'{file_name}.txt')  # ??? example.txt

with open(f'{file_name}.txt', 'w', encoding='utf-8') as f:
    f.write('first line' + '\n')
    f.write('second line' + '\n')

var1 = 'fql'
var2 = 'jiyik'

result = f'{var1}{var2}.csv'
print(result)  # ??? fqljiyik.csv

file_name = 'example'

integer = 1234
print(f'{file_name}_{integer}.txt')  # ??? example_1234.txt

with open(f'{file_name}_{integer}.txt', 'w', encoding='utf-8') as f:
    f.write('first line' + '\n')
    f.write('second line' + '\n')

import time
timestamp = int(time.time())

file_name = 'example'

print(f'{file_name}_{timestamp}.txt')  # ??? example_1665817197.txt

with open(f'{file_name}_{timestamp}.txt', 'w', encoding='utf-8') as f:
    f.write('first line' + '\n')
    f.write('second line' + '\n')

import csv
file_name = 'example'

with open(file_name + '.csv', 'w', newline='', encoding='utf-8') as csvfile:
    csv_writer = csv.writer(csvfile, delimiter=',',
                            quoting=csv.QUOTE_MINIMAL)
    csv_writer.writerow(['www', 'jiyik', 'Com'])

print('ab' + 'cd') # ??? abcd

file_name = 123456

result = str(file_name) + '.csv'

print(result) # ??? 123456.csv

file_name = 'example'

print('{}.txt'.format(file_name))  # ??? example.txt

with open('{}.txt'.format(file_name), 'w', encoding='utf-8') as f:
    f.write('first line' + '\n')
    f.write('second line' + '\n')

first = 'fql'
last = 'jiyik'

result = "{}_{}.txt".format(first, last)
print(result)  # ??? "fql_jiyik.txt"

first = 'fql'
last = 'jiyik'

result = "{f}_{l}.txt".format(f=first, l=last)
print(result)  # ??? "fql_jiyik.txt"

import time

first = 'jiyik'

result = "{}_{}.txt".format(first, int(time.time()))
print(result)  # ??? "jiyik_1665817957.txt"