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Questions tagged [concatenation]

Joining of two or more sequences into a single sequence.

Concatenation refers to the joining of two or more elements into a single element.

In programming, this can refer to

  • concatenation, which joins multiple strings into a single string
  • concatenation, where one or more arrays are combined (mostly appended) to make a new array
  • specific concatenation functions that combine elements along a specified dimension (horizontally, or vertically for example), replicate and tile existing elements, and so forth.
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How to concatenate string variables in Bash

In PHP, strings are concatenated together as follows: $foo = "Hello"; $foo .= " World"; Here, $foo becomes "Hello World". How is this accomplished in Bash?
Strawberry
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How do I concatenate two lists in Python?

How do I concatenate two lists in Python? Example: listone = [1, 2, 3] listtwo = [4, 5, 6] Expected outcome: >>> joinedlist [1, 2, 3, 4, 5, 6]
y2k
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How can I concatenate two arrays in Java?

I need to concatenate two String arrays in Java. void f(String[] first, String[] second) { String[] both = ??? } Which is the easiest way to do this?
Antti Kissaniemi
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Can I concatenate multiple MySQL rows into one field?

Using MySQL, I can do something like: SELECT hobbies FROM peoples_hobbies WHERE person_id = 5; My Output: shopping fishing coding but instead I just want 1 row, 1 col: Expected Output: shopping, fishing, coding The reason is that I'm selecting…
Dean Rather
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How to extend an existing JavaScript array with another array, without creating a new array

There doesn't seem to be a way to extend an existing JavaScript array with another array, i.e. to emulate Python's extend method. I want to achieve the following: >>> a = [1, 2] [1, 2] >>> b = [3, 4, 5] [3, 4, 5] >>> SOMETHING HERE >>> a [1, 2, 3,…
Dzinx
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How to concatenate (join) items in a list to a single string

How do I concatenate a list of strings into a single string? For example, given ['this', 'is', 'a', 'sentence'], how do I get "this-is-a-sentence"? For handling a few strings in separate variables, see How do I append one string to another in…
alvas
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StringBuilder vs String concatenation in toString() in Java

Given the 2 toString() implementations below, which one is preferred: public String toString(){ return "{a:"+ a + ", b:" + b + ", c: " + c +"}"; } or public String toString(){ StringBuilder sb = new StringBuilder(100); return…
non sequitor
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Concatenating two std::vectors

How do I concatenate two std::vectors?
yigal
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Pandas Merging 101

How can I perform a (INNER| (LEFT|RIGHT|FULL) OUTER) JOIN with pandas? How do I add NaNs for missing rows after a merge? How do I get rid of NaNs after merging? Can I merge on the index? How do I merge multiple DataFrames? Cross join with…
cs95
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How to concatenate a std::string and an int

I thought this would be really simple, but it's presenting some difficulties. If I have std::string name = "John"; int age = 21; How do I combine them to get a single string "John21"?
Obediah Stane
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Import multiple CSV files into pandas and concatenate into one DataFrame

I would like to read several CSV files from a directory into pandas and concatenate them into one big DataFrame. I have not been able to figure it out though. Here is what I have so far: import glob import pandas as pd # Get data file names path =…
jonas
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How can I get the concatenation of two lists in Python without modifying either one?

In Python, the only way I can find to concatenate two lists is list.extend, which modifies the first list. Is there any concatenation function that returns its result without modifying its arguments?
Ryan C. Thompson
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Getting current date and time in JavaScript

I have a script that prints the current date and time in JavaScript, but the DATE is always wrong. Here is the code: var currentdate = new Date(); var datetime = "Last Sync: " + currentdate.getDay() + "/" + currentdate.getMonth() + "/" +…
Ricardo
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String concatenation: concat() vs "+" operator

Assuming String a and b: a += b a = a.concat(b) Under the hood, are they the same thing? Here is concat decompiled as reference. I'd like to be able to decompile the + operator as well to see what that does. public String concat(String s) { …
shsteimer
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Concatenate multiple files but include filename as section headers

I would like to concatenate a number of text files into one large file in terminal. I know I can do this using the cat command. However, I would like the filename of each file to precede the "data dump" for that file. Anyone know how to do…
Nick
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