Issue #12760: Add a create mode to open(). Patch by David Townshend.
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 @@
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 @@
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 @@
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 @@
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 @@
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 @@
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)