conditional-operator

问题 I have the following data frame: >>> import pandas as pd >>> import numpy as np >>> df_test = pd.DataFrame({'id': [100, 101, 102, 103, 104], 'drive': ['4WD', None, '4WD', None, '2WD']}) >>> print(df_test) id drive 0 100 4WD 1 101 None 2 102 4WD 3 103 None 4 104 2WD And I would like to make a new column is_4x4 , that would be equal to 0, when drive is None , or drive is 2WD . In other cases, I would like the column to be equal to 1. I am using the following code, but the result is not as I

问题 I have the following data frame: >>> import pandas as pd >>> import numpy as np >>> df_test = pd.DataFrame({'id': [100, 101, 102, 103, 104], 'drive': ['4WD', None, '4WD', None, '2WD']}) >>> print(df_test) id drive 0 100 4WD 1 101 None 2 102 4WD 3 103 None 4 104 2WD And I would like to make a new column is_4x4 , that would be equal to 0, when drive is None , or drive is 2WD . In other cases, I would like the column to be equal to 1. I am using the following code, but the result is not as I

问题 This question already has answers here : Closed 8 years ago . Possible Duplicate: Python Check if all of the following items is in a list So I want to test whether both word and word1 are in the list lst. Of course, I could write: if word in lst and word1 in lst: do x But I wondered if I could shorten that statement to something like: if (word and word1) in lst: do x Of course, that does not work, but is there anything effectively similar that will? I tried the following, but as you can see,

问题 This question already has answers here : Closed 8 years ago . Possible Duplicate: Python Check if all of the following items is in a list So I want to test whether both word and word1 are in the list lst. Of course, I could write: if word in lst and word1 in lst: do x But I wondered if I could shorten that statement to something like: if (word and word1) in lst: do x Of course, that does not work, but is there anything effectively similar that will? I tried the following, but as you can see,

问题 this code doesn't work int main(){ cout << 5 ? (5 ? 0 : 2) : 5; system("pause"); return 0; } this code works int main(){ cout << (5 ? (5 ? 0 : 2) : 5); system("pause"); return 0; } can't understand why? 回答1: cout << 5 ? (5 ? 0 : 2) : 5; is parsed as (cout << 5) ? (5 ? 0 : 2) : 5; 回答2: This is due to operator precedence rules. << has higher precedence than ? , so your first expression is parsed as: (cout << 5) ? (5 ? 0 : 2) : 5; Brackets are necessary in this case to get the parse you want. 来源

问题 In JavaScript, what is the difference between using true ? 'Hello' : 'Goodbye' //Evaluates to "Hello" false ? 'Hello' : 'Goodbye' //Evaluates to "Goodbye" and true && 'Hello' || 'Goodbye' //Evaluates to "Hello" false && 'Hello' || 'Goodbye' //Evaluates to "Goodbye" 回答1: These are two different concepts that happen to give you the same answer. The first example uses the ternary operator and its result depends only on the first operand (in your example true / false ): true ? 'Hello' : 'Goodbye'

问题 I have the below RSS to parse, something like: <?xml version="1.0" encoding="utf-8"?> <rss xmlns:x-wr="http://www.w3.org/2002/12/cal/prod/Apple_Comp_628d9d8459c556fa#" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:x-example="http://www.example.com/rss/x-example" xmlns:x-microsoft="http://schemas.microsoft.com/x-microsoft" xmlns:xCal="urn:ietf:params:xml:ns:xcal" version="2.0"> <channel> <item> <title>About Apples</title> <author>David

问题 I have two methods in the Item Class: public void setValue(String v); public void setValue(Double v); and I want to use Conditional Operator to setVAlue in another class: String str = ... Double dbl = ... item.setValue((condition) ? str : dbl); but compiler says: cannot find symbol symbol : method setValue(java.lang.Object&java.io.Serializable&java.lang.Comparable<? extends java.lang.Object&java.io.Serializable&java.lang.Comparable<?>>) I think compiler uses the nearest common superclass

问题 I have two methods in the Item Class: public void setValue(String v); public void setValue(Double v); and I want to use Conditional Operator to setVAlue in another class: String str = ... Double dbl = ... item.setValue((condition) ? str : dbl); but compiler says: cannot find symbol symbol : method setValue(java.lang.Object&java.io.Serializable&java.lang.Comparable<? extends java.lang.Object&java.io.Serializable&java.lang.Comparable<?>>) I think compiler uses the nearest common superclass

问题 I have two methods in the Item Class: public void setValue(String v); public void setValue(Double v); and I want to use Conditional Operator to setVAlue in another class: String str = ... Double dbl = ... item.setValue((condition) ? str : dbl); but compiler says: cannot find symbol symbol : method setValue(java.lang.Object&java.io.Serializable&java.lang.Comparable<? extends java.lang.Object&java.io.Serializable&java.lang.Comparable<?>>) I think compiler uses the nearest common superclass