arquivos.md

Arquivos

open

Read

filename = 'hello_world.py'
f = open(filename, 'r', encoding='ascii')

print("conteúdo " + filename)
print('-' * 30)
for line in f:
    print(line, end='')

f.close()

# usando 'with'
filename = 'while_loop.py'

print("\n\n conteúdo " + filename)
print('-' * 30)
with open(filename, 'r', encoding='ascii') as f:
    for line in f:
        print(line, end='')

• arquivo nao existe

with open('xyz.py', 'r', encoding='ascii') as f:
    for line in f:
        print(line, end='')

• ler todo conteúdo para uma string

>>> f = open('hello_world.py', 'r', encoding='ascii')
>>> f
<_io.TextIOWrapper name='hello_world.py' mode='r' encoding='ascii'>
>>> print(f.read())

• linha por linha usando readline()

>>> f = open('hello_world.py', 'r', encoding='ascii')
>>> print(f.readline(), end='')
>>> print(f.readline(), end='')
>>> print(f.readline(), end='')

>>> f.close()
>>> print(f.readline(), end='')
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
ValueError: I/O operation on closed file.

• lendo todas as linhas com readlines()

>>> f = open('hello_world.py', 'r', encoding='ascii')
>>> all_lines = f.readlines()
>>> all_lines
['#!/usr/bin/python3\n', '\n', 'print("Hello World")\n']

• verificar se arquivo fechado

>>> f = open('hello_world.py', 'r', encoding='ascii')

>>> f.closed
False

>>> f.close()
>>> f.closed
True

escrever arquivos

with open('new_file.txt', 'w', encoding='ascii') as f:
    f.write("linha 1\n")
    f.write("linha 1\n")

$ ./file_writing.py
$ cat new_file.txt 
This is a sample line of text
Yet another line

editando com fileinput

import fileinput

with fileinput.input(inplace=True) as f:
    for line in f:
        line = line.replace('line of text', 'line')
        print(line, end='')

$ ./inplace_file_editing.py new_file.txt
$ cat new_file.txt