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 =r’C:\DRO\DCL_rawdata_files’ filenames = glob.glob(path + “/*.csv”) … Read more
This question already has answers here: How do I concatenate two lists in Python? (31 answers) Closed 6 years ago. 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? 7 s 7 … Read more
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”? 24 s 24 In alphabetical order: std::string name = “John”; int age = 21; std::string result; // 1. with Boost result … Read more
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 pandas merge? join? concat? update? Who? What? Why?! … … Read more
How do I concatenate two std::vectors? 26 s 26 vector1.insert( vector1.end(), vector2.begin(), vector2.end() );
How do I concatenate a list of strings into a single string? [‘this’, ‘is’, ‘a’, ‘sentence’] → ‘this-is-a-sentence’ 1Best Answer 11 Use str.join: >>> sentence = [‘this’, ‘is’, ‘a’, ‘sentence’] >>> ‘-‘.join(sentence) ‘this-is-a-sentence’ >>> ‘ ‘.join(sentence) ‘this is a sentence’
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 sb.append(“{a:”).append(a) .append(“, b:”).append(b) .append(“, c:”).append(c) .append(“}”) .toString(); } ? More importantly, given we have only 3 … Read more
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, 4, 5] I … Read more
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? 6 65
No, not quite. Firstly, there’s a slight difference in semantics. If a is null, then a.concat(b) throws a NullPointerException but a+=b will treat the original value of a as if it were null. Furthermore, the concat() method only accepts String values while the + operator will silently convert the argument to a String (using the … Read more
