Meaning
This pattern wraps a binary file opened in 'rb' mode with a UTF-8 decoder to produce a text stream for reading Unicode data. It is used when you need to read a binary file as text with a specific encoding without loading the entire file into memory.
Primary Function
Text decoding / I/O handling
Communicative Purpose
Enables reading Unicode text from binary streams without manual byte-by-byte decoding.
Pattern
codecs.getreader(encoding)(open(filename, mode))
Core Structure
codecs.getreader(...)(open(...))
Função primária
Text decoding / I/O handling
Propósito comunicativo
Enables reading Unicode text from binary streams without manual byte-by-byte decoding.
Situações de gatilho
File processing: reading a UTF-8 encoded log file stored as binary; Network programming: processing a socket that returns raw bytes; Data ingestion: reading a binary file that contains encoded text data.
Contextos
Python standard library, data processing scripts, file I/O modules.
Padrão
codecs.getreader(encoding)(open(filename, mode))
Estrutura central
codecs.getreader(...)(open(...))
Slots de substituição
encoding: str (e.g., 'utf-8'), filename: str, mode: str (typically 'rb')
Colocados típicos
- with statement
- .read()
- .readline()
- iteration over lines
Substituições comuns
- open(filename
- mode
- encoding=encoding) in Python 3
- io.TextIOWrapper(open(...)
- encoding)
- codecs.open(filename
- mode
- encoding)
Erros comuns
Passing a text stream instead of a binary stream: causes double-decoding errors and garbled output; Using mode 'r' instead of 'rb': open returns a text stream which getreader cannot wrap, raising TypeError; Forgetting to close the file: leaks file descriptors since the wrapper does not auto-close without a with statement; Assuming platform default encoding: produces incorrect results on systems with non-UTF-8 locale defaults.
Similar / contraste
codecs.open(filename, mode, encoding) (directly opens text file); io.BufferedReader vs TextIOWrapper.
Interferências
Coming from Java: BufferedReader with InputStreamReader handles decoding transparently — Python's codecs.getreader requires explicit encoding argument and a binary stream → always pass encoding and ensure the underlying stream is opened in binary mode.
Família do chunk
- codecs.getreader
- codecs.getwriter
- codecs.open
- io.TextIOWrapper
Nuance
The returned reader expects a binary stream; passing a text stream will cause double-decoding. Not suitable for writing; use codecs.getwriter for writing.
Efeito pragmático
Makes encoding handling explicit and avoids accidental decoding errors.
Dica de memória
Wrap binary stream with getreader to read text.
Nota
In Python 3, prefer open with encoding parameter; codecs.getreader is mostly for legacy or when you need to wrap an existing binary stream.
Upgrade path
Using io.TextIOWrapper or open with encoding parameter
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