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String concatenation vs. string substitution in Python
In Python, the where and when of using string concatenation versus string substitution eludes me. As the string concatenation has seen large boosts in performance, is this (becoming more) a stylistic decision rather than a practical one?
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Large, persistent DataFrame in pandas
...o read the file in smaller pieces (use iterator=True, chunksize=1000) then concatenate then with pd.concat. The problem comes in when you pull the entire text file into memory in one big slurp.
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Concat all strings inside a List using LINQ
Is there any easy LINQ expression to concatenate my entire List<string> collection items to a single string with a delimiter character?
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Spring JPA @Query with LIKE
...orks for me):
@Query("SELECT u.username FROM User u WHERE u.username LIKE CONCAT('%',:username,'%')")
List<String> findUsersWithPartOfName(@Param("username") String username);
Notice: The table name in JPQL must start with a capital letter.
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StringBuilder vs String concatenation in toString() in Java
...s it might not make a
difference, but at what point do you
switch from concat to builder?
At the point where you're concatenating in a loop - that's usually when the compiler can't substitute StringBuilder by itself.
s...
How do I quickly rename a MySQL database (change schema name)?
...ginally suggested the former and someone "improved" my answer to use GROUP_CONCAT. Take your pick, but I prefer the original):
SELECT CONCAT('RENAME TABLE $1.', table_name, ' TO $2.', table_name, '; ')
FROM information_schema.TABLES
WHERE table_schema='$1';
or
SELECT GROUP_CONCAT('RENAME TABLE ...
What's the best name for a non-mutating “add” method on an immutable collection?
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In situations like that, I usually go with Concat. That usually implies to me that a new object is being created.
var p = listA.Concat(listB);
var k = listA.Concat(item);
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MySQL JOIN the most recent row only?
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You may want to try the following:
SELECT CONCAT(title, ' ', forename, ' ', surname) AS name
FROM customer c
JOIN (
SELECT MAX(id) max_id, customer_id
FROM customer_data
GROUP BY customer_id
) c...
Why use pointers? [closed]
...inter points to nothing
}
//now, let's allocate some memory
p = new MyType[50000];
if(p) //if the memory was allocated, this test will pass
{
//we can do something with our allocated array
for(size_t i=0; i!=50000; i++)
{
MyType &v = *(p+i); //get a reference to the ith objec...
How is null + true a string?
...e compiler, it's actually able to compile the above as:
string x = string.Concat(a, b, c, d);
which can create just a single string of exactly the right length, copying all the data exactly once. Nice.
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