readline
— GNU Readline 接口
¶
readline
module defines a number of functions to facilitate completion and reading/writing of history files from the Python interpreter. This module can be used directly, or via the
rlcompleter
module, which supports completion of Python identifiers at the interactive prompt. Settings made using this module affect the behaviour of both the interpreter’s interactive prompt and the prompts offered by the built-in
input()
函数。
注意
The underlying Readline library API may be implemented by the
libedit
library instead of GNU readline. On MacOS X the
readline
module detects which library is being used at run time.
The configuration file for
libedit
is different from that of GNU readline. If you programmatically load configuration strings you can check for the text “libedit” in
readline.__doc__
to differentiate between GNU readline and libedit.
Readline keybindings may be configured via an initialization file, typically
.inputrc
in your home directory. See
Readline 初始文件
in the GNU Readline manual for information about the format and allowable constructs of that file, and the capabilities of the Readline library in general.
下列函数涉及初始文件和用户配置：
readline.
parse_and_bind
(
string
)
¶
Execute the init line provided in the
string
argument. This calls
rl_parse_and_bind()
在底层库中。
readline.
read_init_file
(
[
filename
]
)
¶
Execute a readline initialization file. The default filename is the last filename used. This calls
rl_read_init_file()
在底层库中。
下列函数操作行缓冲:
readline.
get_line_buffer
(
)
¶
Return the current contents of the line buffer (
rl_line_buffer
in the underlying library).
readline.
insert_text
(
string
)
¶
Insert text into the line buffer at the cursor position. This calls
rl_insert_text()
in the underlying library, but ignores the return value.
readline.
redisplay
(
)
¶
Change what’s displayed on the screen to reflect the current contents of the line buffer. This calls
rl_redisplay()
在底层库中。
下列函数操作历史文件:
readline.
read_history_file
(
[
filename
]
)
¶
Load a readline history file, and append it to the history list. The default filename is
~/.history
。这会调用
read_history()
在底层库中。
readline.
write_history_file
(
[
filename
]
)
¶
Save the history list to a readline history file, overwriting any existing file. The default filename is
~/.history
。这会调用
write_history()
在底层库中。
readline.
append_history_file
(
nelements
[
,
filename
]
)
¶
Append the last
nelements
items of history to a file. The default filename is
~/.history
. The file must already exist. This calls
append_history()
in the underlying library. This function only exists if Python was compiled for a version of the library that supports it.
3.5 版新增。
readline.
get_history_length
(
)
¶
readline.
set_history_length
(
length
)
¶
Set or return the desired number of lines to save in the history file.
write_history_file()
function uses this value to truncate the history file, by calling
history_truncate_file()
in the underlying library. Negative values imply unlimited history file size.
下列函数操作全局历史列表:
readline.
clear_history
(
)
¶
Clear the current history. This calls
clear_history()
in the underlying library. The Python function only exists if Python was compiled for a version of the library that supports it.
readline.
get_current_history_length
(
)
¶
Return the number of items currently in the history. (This is different from
get_history_length()
, which returns the maximum number of lines that will be written to a history file.)
readline.
get_history_item
(
index
)
¶
Return the current contents of history item at
index
. The item index is one-based. This calls
history_get()
在底层库中。
readline.
remove_history_item
(
pos
)
¶
Remove history item specified by its position from the history. The position is zero-based. This calls
remove_history()
在底层库中。
readline.
replace_history_item
(
pos
,
line
)
¶
Replace history item specified by its position with
line
. The position is zero-based. This calls
replace_history_entry()
在底层库中。
readline.
add_history
(
line
)
¶
追加
line
to the history buffer, as if it was the last line typed. This calls
add_history()
在底层库中。
readline.
set_auto_history
(
enabled
)
¶
Enable or disable automatic calls to
add_history()
when reading input via readline. The
enabled
argument should be a Boolean value that when true, enables auto history, and that when false, disables auto history.
3.6 版新增。
CPython 实现细节： Auto history is enabled by default, and changes to this do not persist across multiple sessions.
readline.
set_startup_hook
(
[
function
]
)
¶
Set or remove the function invoked by the
rl_startup_hook
callback of the underlying library. If
function
is specified, it will be used as the new hook function; if omitted or
None
, any function already installed is removed. The hook is called with no arguments just before readline prints the first prompt.
readline.
set_pre_input_hook
(
[
function
]
)
¶
Set or remove the function invoked by the
rl_pre_input_hook
callback of the underlying library. If
function
is specified, it will be used as the new hook function; if omitted or
None
, any function already installed is removed. The hook is called with no arguments after the first prompt has been printed and just before readline starts reading input characters. This function only exists if Python was compiled for a version of the library that supports it.
The following functions relate to implementing a custom word completion function. This is typically operated by the Tab key, and can suggest and automatically complete a word being typed. By default, Readline is set up to be used by
rlcompleter
to complete Python identifiers for the interactive interpreter. If the
readline
module is to be used with a custom completer, a different set of word delimiters should be set.
readline.
set_completer
(
[
function
]
)
¶
Set or remove the completer function. If
function
is specified, it will be used as the new completer function; if omitted or
None
, any completer function already installed is removed. The completer function is called as
function(text,
state)
, for
state
in
0
,
1
,
2
, …, until it returns a non-string value. It should return the next possible completion starting with
text
.
The installed completer function is invoked by the
entry_func
callback passed to
rl_completion_matches()
在底层库中。
text
string comes from the first parameter to the
rl_attempted_completion_function
callback of the underlying library.
readline.
get_completer
(
)
¶
Get the completer function, or
None
if no completer function has been set.
readline.
get_completion_type
(
)
¶
Get the type of completion being attempted. This returns the
rl_completion_type
variable in the underlying library as an integer.
readline.
get_begidx
(
)
¶
readline.
get_endidx
(
)
¶
Get the beginning or ending index of the completion scope. These indexes are the
start
and
end
arguments passed to the
rl_attempted_completion_function
callback of the underlying library.
readline.
set_completer_delims
(
string
)
¶
readline.
get_completer_delims
(
)
¶
Set or get the word delimiters for completion. These determine the start of the word to be considered for completion (the completion scope). These functions access the
rl_completer_word_break_characters
variable in the underlying library.
readline.
set_completion_display_matches_hook
(
[
function
]
)
¶
Set or remove the completion display function. If
function
is specified, it will be used as the new completion display function; if omitted or
None
, any completion display function already installed is removed. This sets or clears the
rl_completion_display_matches_hook
callback in the underlying library. The completion display function is called as
function(substitution,
[matches],
longest_match_length)
once each time matches need to be displayed.
以下范例演示如何使用
readline
模块的历史读写功能，去自动加载和保存历史文件
.python_history
from the user’s home directory. The code below would normally be executed automatically during interactive sessions from the user’s
PYTHONSTARTUP
文件。
import atexit
import os
import readline
histfile = os.path.join(os.path.expanduser("~"), ".python_history")
try:
readline.read_history_file(histfile)
# default history len is -1 (infinite), which may grow unruly
readline.set_history_length(1000)
except FileNotFoundError:
pass
atexit.register(readline.write_history_file, histfile)
此代码实际会自动运行，当 Python 运行在 交互模式 (见 Readline 配置 ).
The following example achieves the same goal but supports concurrent interactive sessions, by only appending the new history.
import atexit
import os
import readline
histfile = os.path.join(os.path.expanduser("~"), ".python_history")
try:
readline.read_history_file(histfile)
h_len = readline.get_current_history_length()
except FileNotFoundError:
open(histfile, 'wb').close()
h_len = 0
def save(prev_h_len, histfile):
new_h_len = readline.get_current_history_length()
readline.set_history_length(1000)
readline.append_history_file(new_h_len - prev_h_len, histfile)
atexit.register(save, h_len, histfile)
以下范例扩展了
code.InteractiveConsole
类以支持历史的保存/还原。
import atexit
import code
import os
import readline
class HistoryConsole(code.InteractiveConsole):
def __init__(self, locals=None, filename="<console>",
histfile=os.path.expanduser("~/.console-history")):
code.InteractiveConsole.__init__(self, locals, filename)
self.init_history(histfile)
def init_history(self, histfile):
readline.parse_and_bind("tab: complete")
if hasattr(readline, "read_history_file"):
try:
readline.read_history_file(histfile)
except FileNotFoundError:
pass
atexit.register(self.save_history, histfile)
def save_history(self, histfile):
readline.set_history_length(1000)
readline.write_history_file(histfile)