In Dateien schreiben und an sie anhängen

Einführung

Schreibmodus 'w'

# with open('out.txt', 'w') as f:
#     f.write('Hello, World!')
print('write mode demo')

writelines()

lines = ['line1\n', 'line2\n']
# with open('out.txt', 'w') as f:
#     f.writelines(lines)
print('writelines demo')

Anhängemodus 'a'

# with open('log.txt', 'a') as f:
#     f.write('new entry\n')
print('append mode demo')

Zeilenumbrüche in write()

# with open('out.txt', 'w') as f:
#     f.write('first line\n')
#     f.write('second line\n')
print('newline demo')

Lese- und Schreibmodus 'r+'

# with open('out.txt', 'r+') as f:
#     f.seek(0, 2)  # go to end
#     f.write('appended')
print('r+ demo')

Puffer leeren

# with open('log.txt', 'a') as f:
#     f.write('event\n')
#     f.flush()
print('flush demo')

print() in Dateien

# with open('out.txt', 'w') as f:
#     print('Hello', file=f)
print('print-to-file demo')

Muster für atomare Schreibvorgänge

import tempfile, os
# with tempfile.NamedTemporaryFile('w', delete=False) as f:
#     f.write(data); tmp = f.name
# os.replace(tmp, 'out.txt')
print('atomic write demo')

JSON in eine Datei

import json
data = {'name': 'Alice', 'age': 30}
# with open('data.json', 'w') as f:
#     json.dump(data, f, indent=2)
print(json.dumps(data, indent=2))

Binärer Schreibmodus 'wb'

# with open('out.bin', 'wb') as f:
#     f.write(bytes([0, 255, 128]))
print('binary write demo')

Schnellüberprüfung

Zusammenfassung

Weiter