Python basic grammar note (4)

at first

This is a memo while studying python I will add various things in the future

File operations and system

File creation

# Open and close the file
f = open('text.text', 'w')
f.write('Text\n')
f.close()

Open the file with the with statement

with open('text.text', 'w') as f:
    f.write('Test\n')

Read file

# By chunk
with open('text.text', 'r') as f:
    while True:
        chunk = 2
        line = f.read(chunk)
        print(line)
        if not line:
            break
         
>>Te
>>st

 (Test is entered in the text.text file)

Use seek to move

s = """\
AAA
BBB
CCC
"""

with open('text.text', 'r') as f:
    print(f.tell())
    print(f.read(1))
    f.seek(5)

>>>0
>>>A

Write / read mode

s = """\
AAA
BBB
CCC
EEE
"""

with open('text.text', 'r+') as f:
    print(f.read())
    f.seek(0)
    f.write(s)

# Also written to the text.text file
AAA
BBB
CCC
EEE

template

import string

s = """\

Hi $name

$contents

Have a good day

"""

t = string.Template(s)
contents = t.substitute(name='Mike', contents='How are you')
print(contents)

>>>Hi Mike
>>>How are you
>>>Have a good day

Write and read to CSV file

import csv

with open('text.csv,', 'w') as csv_file:
    fieldnames = ['Name', 'Count']
    writer = csv.DictWriter(csv_file, fieldnames=fieldnames)
    writer.writeheader()
    writer.writerow({'Name': 'A', 'Count': 1})
    writer.writerow({'Name': 'B', 'Count': 2})

with open('test.csv', 'r') as csv_file:
    reader = csv.DictReader(csv)
    for row in reader:
        print(row['Name'], row['Count'])

File operations

import os
import pathlib
import glob
import shutil

# Whether there is text.text
print(os.path.exists('text.text'))
>>>True

# Check if it is a file
print(os.path.isfile('text.text'))

# Is it a directory?
print(print(os.path.isdir('sample_codes')))

# Rename the file
os.rename('text.text', 'renamed.text')

# Simulink link
os.symlink('renamed.text', 'symlink.txt')

# Create a directory
os.mkdir('test.dir')

# Erase the directory
os.rmdir('test.dir')

# Create a file
pathlib.Path('empty.txt').touch()

# Erase files
os.remove('empty.txt')

# View the list of directories
os.mkdir('test_dir')
os.mkdir('test_dir/test_dir2')
print(os.listdir('test_dir'))

# What kind of files are there
pathlib.Path('test_dir/test_dir2/empty.txt').touch()

# View all files
print(glob.glob('test_dir/test_dir2/*'))

# make a copy
shutil.copy('test_dir/test_dir2/empty.txt','test_dir/test_dir2/empty2.txt')

# Erase all directories
shutil.rmtree('test_dir')

# I want to know the location of the directory
print(os.getcwd())

Compress and decompress tarfile

import tarfile

with tarfile.open('test.tar.gz', 'w:gz') as tr:
    tr.add('test_dir')

# Deploy with python
with tarfile.open('test.tar.gz', 'r:gz') as tr:
    tr.extractall(path='test_dir')

# If you want to see only the contents
with tarfile.open('test.tar.gz', 'r:gz') as tr:
    with tr.extractall('test_dir/sub_dir/sub_test.txt') as f:
        print(f.read())

Compress and decompress zipfile

import glob
import zipfile


with zipfile.ZipFile('text.zip', 'w') as z:
    z.write('test_dir')
    z.write('test_dir/text.txt')
    for f in glob.glob('text_dir/**', recursive=True):
        z.write(f)

with zipfile.ZipFile('test.zip', 'r') as z:
    z.extractall('zzz2')
    with z.open('text_dir/text.txt') as f:
        print(f.read())

What is tempfile

import tempfile

# Temporarily generate a file
with tempfile.TemporaryFile(mode='w+') as t:
    t.write('hello')
    t.seek(0)
    print(t.read())

# Actually create the file
with tempfile.NamedTemporaryFile(delete=False) as t:
    print(t.name)
    with open(t.name, '+w') as f:
        f.write('test\n')
        f.seek(0)
        print(f.read())

with tempfile.TemporaryDirectory() as td:
    print(td)

temp_dir = tempfile.mkdtemp()
print(temp_dir)

Execute command in subprocess

import subprocess

subprocess.run(['ls', '-al'])

What is datetime

import datetime

now = datetime.datetime.now()
print(now)
print(now.isoformat())
print(now.strftime('%d/%m/%y'))

today = datetime.date.today()
print(today.isoformat())
print(today.strftime('%d/%m/%y'))