diff options
Diffstat (limited to 'Lib/_pyio.py')
| -rw-r--r-- | Lib/_pyio.py | 34 |
1 files changed, 19 insertions, 15 deletions
diff --git a/Lib/_pyio.py b/Lib/_pyio.py index fcd548d..6e8f369 100644 --- a/Lib/_pyio.py +++ b/Lib/_pyio.py @@ -38,21 +38,22 @@ def open(file, mode="r", buffering=-1, encoding=None, errors=None, wrapped. (If a file descriptor is given, it is closed when the returned I/O object is closed, unless closefd is set to False.) - mode is an optional string that specifies the mode in which the file - is opened. It defaults to 'r' which means open for reading in text - mode. Other common values are 'w' for writing (truncating the file if - it already exists), and 'a' for appending (which on some Unix systems, - means that all writes append to the end of the file regardless of the - current seek position). In text mode, if encoding is not specified the - encoding used is platform dependent. (For reading and writing raw - bytes use binary mode and leave encoding unspecified.) The available - modes are: + mode is an optional string that specifies the mode in which the file is + opened. It defaults to 'r' which means open for reading in text mode. Other + common values are 'w' for writing (truncating the file if it already + exists), 'x' for creating and writing to a new file, and 'a' for appending + (which on some Unix systems, means that all writes append to the end of the + file regardless of the current seek position). In text mode, if encoding is + not specified the encoding used is platform dependent. (For reading and + writing raw bytes use binary mode and leave encoding unspecified.) The + available modes are: ========= =============================================================== Character Meaning --------- --------------------------------------------------------------- 'r' open for reading (default) 'w' open for writing, truncating the file first + 'x' create a new file and open it for writing 'a' open for writing, appending to the end of the file if it exists 'b' binary mode 't' text mode (default) @@ -63,7 +64,8 @@ def open(file, mode="r", buffering=-1, encoding=None, errors=None, The default mode is 'rt' (open for reading text). For binary random access, the mode 'w+b' opens and truncates the file to 0 bytes, while - 'r+b' opens the file without truncation. + 'r+b' opens the file without truncation. The 'x' mode implies 'w' and + raises an `FileExistsError` if the file already exists. Python distinguishes between files opened in binary and text modes, even when the underlying operating system doesn't. Files opened in @@ -154,8 +156,9 @@ def open(file, mode="r", buffering=-1, encoding=None, errors=None, if errors is not None and not isinstance(errors, str): raise TypeError("invalid errors: %r" % errors) modes = set(mode) - if modes - set("arwb+tU") or len(mode) > len(modes): + if modes - set("axrwb+tU") or len(mode) > len(modes): raise ValueError("invalid mode: %r" % mode) + creating = "x" in modes reading = "r" in modes writing = "w" in modes appending = "a" in modes @@ -163,14 +166,14 @@ def open(file, mode="r", buffering=-1, encoding=None, errors=None, text = "t" in modes binary = "b" in modes if "U" in modes: - if writing or appending: + if creating or writing or appending: raise ValueError("can't use U and writing mode at once") reading = True if text and binary: raise ValueError("can't have text and binary mode at once") - if reading + writing + appending > 1: + if creating + reading + writing + appending > 1: raise ValueError("can't have read/write/append mode at once") - if not (reading or writing or appending): + if not (creating or reading or writing or appending): raise ValueError("must have exactly one of read/write/append mode") if binary and encoding is not None: raise ValueError("binary mode doesn't take an encoding argument") @@ -179,6 +182,7 @@ def open(file, mode="r", buffering=-1, encoding=None, errors=None, if binary and newline is not None: raise ValueError("binary mode doesn't take a newline argument") raw = FileIO(file, + (creating and "x" or "") + (reading and "r" or "") + (writing and "w" or "") + (appending and "a" or "") + @@ -205,7 +209,7 @@ def open(file, mode="r", buffering=-1, encoding=None, errors=None, raise ValueError("can't have unbuffered text I/O") if updating: buffer = BufferedRandom(raw, buffering) - elif writing or appending: + elif creating or writing or appending: buffer = BufferedWriter(raw, buffering) elif reading: buffer = BufferedReader(raw, buffering) |