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What is the preferred syntax for initializing a dict: curly brace literals {} or the dict() function
...e keys are valid Python identifiers.
This works:
a = {'import': 'trade', 1: 7.8}
a = dict({'import': 'trade', 1: 7.8})
This won't work:
a = dict(import='trade', 1=7.8)
>> SyntaxError: invalid syntax ^
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Bash script error [: !=: unary operator expected
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189
Quotes!
if [ "$1" != -v ]; then
Otherwise, when $1 is completely empty, your test becomes:
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Retrieving the last record in each group - MySQL
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1021
MySQL 8.0 now supports windowing functions, like almost all popular SQL implementations. With...
Return index of greatest value in an array
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12 Answers
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Creating a zero-filled pandas data frame
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140
You can try this:
d = pd.DataFrame(0, index=np.arange(len(data)), columns=feature_list)
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Nginx url重写rewrite实例详解 - 更多技术 - 清泛网移动版 - 专注C/C++及内核技术
...rewrite在nginx中实现url重写，学习rewrite的具体用法，包括301重定向的内容等，希望对大家有所帮助。nginx rewrite 实现二级域名跳转
当访问http://www.jbyuan.com跳转到http://www.jbyuan.com/nvxingjiankang/
方法一：
这种方法浏览器地址会变www.j...
How can I convert spaces to tabs in Vim or Linux?
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318
Using Vim to expand all leading spaces (wider than 'tabstop'), you were right to use retab but ...
Take the content of a list and append it to another list
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You probably want
list2.extend(list1)
instead of
list2.append(list1)
Here's the difference:
>>> a = range(5)
>>> b = range(3)
>>> c = range(2)
>>> b.append(a)
>>> b
[0, 1, 2, [0, 1, 2, 3, 4]]
>>> c.ex...
How do I test if a variable is a number in Bash?
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How to use a variable for the key part of a map
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169
Use this:
def map = [(A):1, (X):2]
For the value-part it's even easier, since there is no a...