Questions tagged [string-concatenation]

String concatenation is the operation of joining two character strings end-to-end.

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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's user avatar
2418 votes
48 answers
3.3m views

How to concatenate text from multiple rows into a single text string in SQL Server

Consider a database table holding names, with three rows: Peter Paul Mary Is there an easy way to turn this into a single string of Peter, Paul, Mary?
JohnnyM's user avatar
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1175 votes
30 answers
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Shortcuts in Objective-C to concatenate NSStrings

Are there any shortcuts to (stringByAppendingString:) string concatenation in Objective-C, or shortcuts for working with NSString in general? For example, I'd like to make: NSString *myString = @"...
typeoneerror's user avatar
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983 votes
20 answers
699k views

How to efficiently concatenate strings in go

In Go, a string is a primitive type, which means it is read-only, and every manipulation of it will create a new string. So if I want to concatenate strings many times without knowing the length of ...
Randy Sugianto 'Yuku''s user avatar
972 votes
22 answers
1.9m views

Combine two columns of text in pandas dataframe

I have a dataframe that looks like Year quarter 2000 q2 2001 q3 How do I add a new column by combining these columns to get the following dataframe? Year quarter period 2000 q2 ...
user2866103's user avatar
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954 votes
22 answers
2.3m views

How do I concatenate strings and variables in PowerShell?

Suppose I have the following snippet: $assoc = New-Object PSObject -Property @{ Id = 42 Name = "Slim Shady" Owner = "Eminem" } Write-Host $assoc.Id + " - " ...
Ninja Cowgirl's user avatar
587 votes
9 answers
475k views

How do I concatenate strings?

How do I concatenate the following combinations of types: str and str String and str String and String
jsalter's user avatar
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547 votes
11 answers
528k views

How to concatenate strings in twig

Anyone knows how to concatenate strings in twig? I want to do something like: {{ concat('http://', app.request.host) }}
stoefln's user avatar
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494 votes
23 answers
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How to use GROUP BY to concatenate strings in SQL Server?

How do I get: id Name Value 1 A 4 1 B 8 2 C 9 to id Column 1 A:4, B:8 2 C:9
Eldila's user avatar
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475 votes
12 answers
925k views

How can two strings be concatenated?

How can I concatenate (merge, combine) two values? For example I have: tmp = cbind("GAD", "AB") tmp # [,1] [,2] # [1,] "GAD" "AB" My goal is to concatenate the two values in "tmp" to one ...
Hans's user avatar
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424 votes
16 answers
191k views

How to keep the spaces at the end and/or at the beginning of a String?

I have to concatenate these two strings from my resource/value files: <string name="Toast_Memory_GameWon_part1">you found ALL PAIRS ! on </string> <string name="...
Hubert's user avatar
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406 votes
17 answers
398k views

Using LINQ to concatenate strings

What is the most efficient way to write the old-school: StringBuilder sb = new StringBuilder(); if (strings.Count > 0) { foreach (string s in strings) { sb.Append(s + ", "); } ...
tags2k's user avatar
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404 votes
16 answers
616k views

String concatenation in Ruby

I am looking for a more elegant way of concatenating strings in Ruby. I have the following line: source = "#{ROOT_DIR}/" << project << "/App.config" Is there a nicer way of doing this? ...
dagda1's user avatar
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293 votes
7 answers
494k views

How to set the id attribute of a HTML element dynamically with angularjs (1.x)?

Provided an HTML element of type div, how to set the value of its id attribute, which is the concatenation of a scope variable and a string ?
Th. Ma.'s user avatar
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256 votes
11 answers
298k views

C++ equivalent of StringBuffer/StringBuilder?

Is there a C++ Standard Template Library class that provides efficient string concatenation functionality, similar to C#'s StringBuilder or Java's StringBuffer?
An̲̳̳drew's user avatar
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241 votes
3 answers
277k views

How to concatenate strings with padding in sqlite

I have three columns in an sqlite table: Column1 Column2 Column3 A 1 1 A 1 2 A 12 2 C 13 2 B ...
Akshara's user avatar
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214 votes
13 answers
174k views

How to create a SQL Server function to "join" multiple rows from a subquery into a single delimited field? [duplicate]

To illustrate, assume that I have two tables as follows: VehicleID Name 1 Chuck 2 Larry LocationID VehicleID City 1 1 New York 2 1 Seattle 3 ...
Templar's user avatar
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213 votes
21 answers
356k views

How do I concatenate strings in Swift?

How to concatenate string in Swift? In Objective-C we do like NSString *string = @"Swift"; NSString *resultStr = [string stringByAppendingString:@" is a new Programming Language"]; or NSString *...
Rajneesh071's user avatar
212 votes
16 answers
113k views

Can I use require("path").join to safely concatenate urls?

Is this safe to use require("path").join to concatenate URLs, for example: require("path").join("http://example.com", "ok"); //returns 'http://example.com/ok' require("path").join("http://example....
Renato Gama's user avatar
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209 votes
15 answers
154k views

Android TextView : "Do not concatenate text displayed with setText"

I am setting text using setText() by following way. prodNameView.setText("" + name); prodOriginalPriceView.setText("" + String.format(getString(R.string.string_product_rate_with_ruppe_sign), "" + ...
Pratik Butani's user avatar
200 votes
6 answers
429k views

What is the string concatenation operator in Oracle?

What is the string concatenation operator in Oracle SQL? Are there any "interesting" features I should be careful of? (This seems obvious, but I couldn't find a previous question asking it).
AJ.'s user avatar
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188 votes
5 answers
163k views

Concatenating null strings in Java [duplicate]

Why does the following work? I would expect a NullPointerException to be thrown. String s = null; s = s + "hello"; System.out.println(s); // prints "nullhello"
yavoh's user avatar
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158 votes
9 answers
521k views

Concatenating string and integer in Python

In Python say you have s = "string" i = 0 print s + i will give you error, so you write print s + str(i) to not get error. I think this is quite a clumsy way to handle int and string ...
specialscope's user avatar
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152 votes
7 answers
315k views

How do you append to an already existing string?

I want append to a string so that every time I loop over it, it will add "test" to the string. Like in PHP you would do: $teststr = "test1\n" $teststr .= "test2\n" echo = ...
Mint's user avatar
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148 votes
13 answers
328k views

const char* concatenation

I need to concatenate two const chars like these: const char *one = "Hello "; const char *two = "World"; How might I go about doing that? I am passed these char*s from a third-party library with a ...
Anthoni Caldwell's user avatar
139 votes
8 answers
224k views

Optimal way to concatenate/aggregate strings

I'm finding a way to aggregate strings from different rows into a single row. I'm looking to do this in many different places, so having a function to facilitate this would be nice. I've tried ...
matt's user avatar
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138 votes
8 answers
206k views

Any reason not to use '+' to concatenate two strings? [duplicate]

A common antipattern in Python is to concatenate a sequence of strings using + in a loop. This is bad because the Python interpreter has to create a new string object for each iteration, and it ends ...
Taymon's user avatar
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129 votes
10 answers
105k views

Why is string concatenation faster than array join?

Today, I read this thread about the speed of string concatenation. Surprisingly, string concatenation was the winner: http://jsben.ch/#/OJ3vo The result was opposite of what I thought. Besides, ...
Sanghyun Lee's user avatar
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115 votes
3 answers
14k views

How is String concatenation implemented in Java 9?

As written in JEP 280: Indify String Concatenation: Change the static String-concatenation bytecode sequence generated by javac to use invokedynamic calls to JDK library functions. This will enable ...
Mohit Tyagi's user avatar
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109 votes
6 answers
204k views

SQL NVARCHAR and VARCHAR Limits

All, I have a large (unavoidable) dynamic SQL query. Due to the number of fields in the selection criteria the string containing the dynamic SQL is growing over 4000 chars. Now, I understand that ...
MoonKnight's user avatar
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107 votes
4 answers
14k views

Is the time-complexity of iterative string append actually O(n^2), or O(n)?

I am working on a problem out of CTCI. The third problem of chapter 1 has you take a string such as 'Mr John Smith ' and asks you to replace the intermediary spaces with %20: 'Mr%20John%...
user5622964's user avatar
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107 votes
3 answers
255k views

String concatenation with Groovy

What is the best (idiomatic) way to concatenate Strings in Groovy? Option 1: calculateAccountNumber(bank, branch, checkDigit, account) { bank + branch + checkDigit + account } Option 2: ...
Arturo Herrero's user avatar
104 votes
7 answers
105k views

JavaScript String concatenation behavior with null or undefined values

As you may know, in JavaScript '' + null = "null" and '' + undefined = "undefined" (in most browsers I can test: Firefox, Chrome and IE). I would like to know the origin of this oddity (what the heck ...
Doc Davluz's user avatar
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102 votes
4 answers
7k views

If Python strings are immutable, why does it keep the same id if I use += to append to it?

Strings in Python are immutable, which means the value cannot be changed. However, when appending to the string in the following example, it looks like the original string memory is modified since the ...
Master_Roshy's user avatar
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100 votes
10 answers
186k views

SQL Server String Concatenation with Null

I am creating a computed column across fields of which some are potentially null. The problem is that if any of those fields is null, the entire computed column will be null. I understand from the ...
Alex's user avatar
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98 votes
9 answers
85k views

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 ...
gotgenes's user avatar
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96 votes
7 answers
96k views

How slow is Python's string concatenation vs. str.join?

As a result of the comments in my answer on this thread, I wanted to know what the speed difference is between the += operator and ''.join() So what is the speed comparison between the two?
Wayne Werner's user avatar
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95 votes
1 answer
114k views

How can I concatenate str and int objects?

If I try to do the following: things = 5 print("You have " + things + " things.") I get the following error in Python 3.x: Traceback (most recent call last): File "<...
Zero Piraeus's user avatar
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90 votes
9 answers
91k views

Best practices/performance: mixing StringBuilder.append with String.concat

I'm trying to understand what the best practice is and why for concatenating string literals and variables for different cases. For instance, if I have code like this StringBuilder sb = new ...
Nick Rolando's user avatar
90 votes
6 answers
194k views

golang convert "type []string" to string

I see some people create a for loop and run through the slice as to create a string, is there an easier way to convert a []string to a string? Will sprintf do it?
user3888307's user avatar
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87 votes
6 answers
101k views

String concatenation without '+' operator

I was playing with python and I realized we don't need to use '+' operator to concatenate static strings. But it fails if I assign it to a variable. For example: string1 = 'Hello' 'World' #1 works ...
ibrahim's user avatar
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85 votes
5 answers
37k views

String concatenation vs. interpolation in Ruby

I am just starting to learn Ruby (first time programming), and have a basic syntactical question with regards to variables, and various ways of writing code. Chris Pine's "Learn to Program" taught ...
Jeff H.'s user avatar
  • 933
84 votes
4 answers
223k views

Concatenating strings doesn't work as expected [closed]

I know it is a common issue, but looking for references and other material I don't find a clear answer to this question. Consider the following code: #include <string> // ... // in a method ...
Andry's user avatar
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81 votes
6 answers
173k views

Getting strings recognized as variable names in R

Related: Strings as variable references in R Possibly related: Concatenate expressions to subset a dataframe I've simplified the question per the comment request. Here goes with some example data. ...
Hendy's user avatar
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76 votes
3 answers
218k views

How to concatenate strings in a Windows batch file?

I have a directory for which I want to list all the .doc files with a ;. I know the following batch command echos all the files: for /r %%i In (*.doc) DO echo %%i But now I want to put them all in ...
Fortega's user avatar
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75 votes
23 answers
478k views

How do I concatenate two strings in Java?

I am trying to concatenate strings in Java. Why isn't this working? public class StackOverflowTest { public static void main(String args[]) { int theNumber = 42; System.out....
test's user avatar
  • 18k
74 votes
2 answers
114k views

Is python += string concatenation bad practice?

I am reading The Hitchhiker’s Guide to Python and there is a short code snippet foo = 'foo' bar = 'bar' foobar = foo + bar # This is good foo += 'ooo' # This is bad, instead you should do: foo = '...
nos's user avatar
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73 votes
6 answers
151k views

Create a comma-separated strings in C#

I have an object which holds many values, and some of them (not all values from the object) need to be put in a CSV string. My approach was this: string csvString = o.number + "," + o.id + &...
grady's user avatar
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67 votes
4 answers
91k views

How to collapse a list of characters into a single string in R

There is a list which I would like to output into an excel file as a single string. I start with a list of characters. url="http://eutils.ncbi.nlm.nih.gov/entrez/eutils/efetch.fcgi?db=pubmed&id=...
userJT's user avatar
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65 votes
8 answers
107k views

How to construct a std::string from a std::vector<string>?

I'd like to build a std::string from a std::vector<std::string>. I could use std::stringsteam, but imagine there is a shorter way: std::string string_from_vector(const std::vector<std::...
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