Python报错'local variable 'analyzer' referenced before assignment',代码里明明有赋值,为什么还提示未定义?
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python UnboundLocalError: local variable ‘x’ referenced before assignment
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python3作用域
python3的作用域和C/C++有所不同 1、 按照L -> E -> G -> B的顺序查找变量 L (Local) 局部作用域 E (Enclosing) 函数外上一层的函数中 G (Global) 全局作用域 B (Built-in) 内建作用域 2、只有在模块module,类class,函数def、lambda中才可以改变作用域,其他情况不可。 例1 def func(): x= 100 print(x) func() print(x) 报错,因为第二个print(x)找不到变量x 例2 for i in range(4): x = i print(x) 正确,因为fo
Python安装包version 3.1.5
This is Python version 3.1.5 ============================ Copyright (c) 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2011, 2012 Python Software Foundation. All rights reserved. Python 3.x is a new version of the language, which is incompatible with the 2.x line of releases. The language is mostly the same, but many details, especially how built-in objects like dictionaries and strings work, have changed considerably, and a lot of deprecated features have finally been removed. Build Instructions ------------------ On Unix, Linux, BSD, OSX, and Cygwin: ./configure make make test sudo make install This will install Python as python3. You can pass many options to the configure script; run "./configure --help" to find out more. On OSX and Cygwin, the executable is called python.exe; elsewhere it's just python. On Mac OS X, if you have configured Python with --enable-framework, you should use "make frameworkinstall" to do the installation. Note that this installs the Python executable in a place that is not normally on your PATH, you may want to set up a symlink in /usr/local/bin. On Windows, see PCbuild/readme.txt. If you wish, you can create a subdirectory and invoke configure from there. For example: mkdir debug cd debug ../configure --with-pydebug make make test (This will fail if you *also* built at the top-level directory. You should do a "make clean" at the toplevel first.) What's New ---------- We try to have a comprehensive overview of the changes in the "What's New in Python 3.1" document, found at http://docs.python.org/3.1/whatsnew/3.1.html For a more detailed change log, read Misc/NEWS (though this file, too, is incomplete, and also doesn't list anything merged in from the 2.7 release under development). If you want to install multiple versions of Python see the section below entitled "Installing multiple versions". Documentation ------------- Documentation for Python 3.1 is online, updated twice a day: http://docs.python.org/3.1/ All documentation is also available online at the Python web site (http://docs.python.org/, see below). It is available online for occasional reference, or can be downloaded in many formats for faster access. The documentation is downloadable in HTML, PostScript, PDF, LaTeX (through 2.5), and reStructuredText (2.6+) formats; the LaTeX and reStructuredText versions are primarily for documentation authors, translators, and people with special formatting requirements. Converting From Python 2.x to 3.x --------------------------------- Python starting with 2.6 will contain features to help locating code that needs to be changed, such as optional warnings when deprecated features are used, and backported versions of certain key Python 3.x features. A source-to-source translation tool, "2to3", can take care of the mundane task of converting large amounts of source code. It is not a complete solution but is complemented by the deprecation warnings in 2.6. See http://docs.python.org/py3k/library/2to3.html for more information. Testing ------- To test the interpreter, type "make test" in the top-level directory. This runs the test set twice (once with no compiled files, once with the compiled files left by the previous test run). The test set produces some output. You can generally ignore the messages about skipped tests due to optional features which can't be imported. If a message is printed about a failed test or a traceback or core dump is produced, something is wrong. On some Linux systems (those that are not yet using glibc 6), test_strftime fails due to a non-standard implementation of strftime() in the C library. Please ignore this, or upgrade to glibc version 6. By default, tests are prevented from overusing resources like disk space and memory. To enable these tests, run "make testall". IMPORTANT: If the tests fail and you decide to mail a bug report, *don't* include the output of "make test". It is useless. Run the failing test manually, as follows: ./python Lib/test/regrtest.py -v test_whatever (substituting the top of the source tree for '.' if you built in a different directory). This runs the test in verbose mode. Installing multiple versions ---------------------------- On Unix and Mac systems if you intend to install multiple versions of Python using the same installation prefix (--prefix argument to the configure script) you must take care that your primary python executable is not overwritten by the installation of a different version. All files and directories installed using "make altinstall" contain the major and minor version and can thus live side-by-side. "make install" also creates ${prefix}/bin/python3 which refers to ${prefix}/bin/pythonX.Y. If you intend to install multiple versions using the same prefix you must decide which version (if any) is your "primary" version. Install that version using "make install". Install all other versions using "make altinstall". For example, if you want to install Python 2.5, 2.6 and 3.0 with 2.6 being the primary version, you would execute "make install" in your 2.6 build directory and "make altinstall" in the others. Issue Tracker and Mailing List ------------------------------ We're soliciting bug reports about all aspects of the language. Fixes are also welcome, preferable in unified diff format. Please use the issue tracker: http://bugs.python.org/ If you're not sure whether you're dealing with a bug or a feature, use the mailing list: python-dev@python.org To subscribe to the list, use the mailman form: http://mail.python.org/mailman/listinfo/python-dev/ Proposals for enhancement ------------------------- If you have a proposal to change Python, you may want to send an email to the comp.lang.python or python-ideas mailing lists for inital feedback. A Python Enhancement Proposal (PEP) may be submitted if your idea gains ground. All current PEPs, as well as guidelines for submitting a new PEP, are listed at http://www.python.org/dev/peps/. Release Schedule ---------------- See PEP 375 for release details: http://www.python.org/dev/peps/pep-0375/ Copyright and License Information --------------------------------- Copyright (c) 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008 Python Software Foundation. All rights reserved. Copyright (c) 2000 BeOpen.com. All rights reserved. Copyright (c) 1995-2001 Corporation for National Research Initiatives. All rights reserved. Copyright (c) 1991-1995 Stichting Mathematisch Centrum. All rights reserved. See the file "LICENSE" for information on the history of this software, terms & conditions for usage, and a DISCLAIMER OF ALL WARRANTIES. This Python distribution contains *no* GNU General Public License (GPL) code, so it may be used in proprietary projects. There are interfaces to some GNU code but these are entirely optional. All trademarks referenced herein are property of their respective holders.
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记录一个关于变量作用域的神奇例子
程序中的变量并不是说访问就能访问的,每个变量都有使用范围,也就是变量都有自己的作用域。看示例1 示例1 b = 3 def f1(a): print(a,b) if __name__ == "__main__": f1(3) #输出结果: 3 3 虽然函数f1中并没有定义b,但是可以使用全部变量b,再看示例2,可能会让你跌眼镜 示例2 b = 3 def f1(a): print(a,b) b = 1 if __name__ == "__main__": f1(3) #UnboundLocalError: local variable 'b' refe
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本文详细解释了在Python中因在函数内部更改全局变量而导致的`local variable referenced before assignment`错误。通过具体代码示例,说明了错误产生的原因及解决方法,即在函数内部使用`global`关键字声明全局变量以避免错误。此外,文章还对比了全局变量和局部变量的作用域差异,强调了系统在访问变量时的查找顺序,帮助读者更好地理解变量作用域的概念及其在实际编程中的应用。
chromedriver-linux64-150.0.7858.0(Canary).zip
chromedriver-linux64-150.0.7858.0(Canary).zip
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