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How to get the first five character of a String
...Empty instead. (It isn't good to combine IsNullOrWhiteSpace with any other test; Instead test for null+empty, then Trim if that is specified behavior, then do whatever tests/operations are needed.)
– ToolmakerSteve
Feb 12 '18 at 16:05
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How to resize a VirtualBox vmdk file
... iso from within the virtualbox settings).
P.S. If your new size is too small, you'll get the same error even with your new vdi file.
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Begin, Rescue and Ensure in Ruby?
...t exception handler. For instance:
begin
raise "Error!!"
rescue
puts "test1"
raise # Reraise exception
ensure
puts "Ensure block"
end
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Ruby regular expression using variable name
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The code you think doesn't work, does:
var = "Value"
str = "a test Value"
p str.gsub( /#{var}/, 'foo' ) # => "a test foo"
Things get more interesting if var can contain regular expression meta-characters. If it does and you want those matacharacters to do what they usually do in...
Why is null an object and what's the difference between null and undefined?
...undefined, null
Booleans: false
Numbers: +0, -0, NaN
Strings: ""
You can test the conversion to boolean by using Boolean as a function (normally it is a constructor, to be used with new):
> Boolean(null)
false
> Boolean("")
false
> Boolean(3-3)
false
> Boolean({})
true
> Boolean([]...
PostgreSQL query to list all table names?
Is there any query available to list all tables in my Postgres DB.
7 Answers
7
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How to use a variable for the database name in T-SQL?
... where did I get the word "SERVERNAME" from?
Here's some code that I just tested (and which works):
DECLARE @DBNAME VARCHAR(255)
SET @DBNAME = 'TestDB'
DECLARE @CREATE_TEMPLATE VARCHAR(MAX)
DECLARE @COMPAT_TEMPLATE VARCHAR(MAX)
DECLARE @RECOVERY_TEMPLATE VARCHAR(MAX)
SET @CREATE_TEMPLATE = 'CREA...
Is it possible to delete an object's property in PHP?
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unset($a->new_property);
This works for array elements, variables, and object attributes.
Example:
$a = new stdClass();
$a->new_property = 'foo';
var_export($a); // -> stdClass::__set_state(array('new_property' => 'foo'))
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关于App Inventor 2过程积木，被问最多的6个问题 - App应用开发 - 清泛IT社...
...>做过程名。完整列表在 <a href="https://en.wikipedia.org/wiki/List_of_Java_keywords" target="_blank">Java关键字列表</a> ，常见的有 <font face="Courier New">if</font>、<font face="Courier New">else</font>、<font face="Courier New">while</font>、<font face="Courier New">for</font...
python pandas dataframe to dictionary
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See the docs for to_dict. You can use it like this:
df.set_index('id').to_dict()
And if you have only one column, to avoid the column name is also a level in the dict (actually, in this case you use the Series.to_dict()):
df.set_index('id')...