lambda

问题 I have a DataFrame: import pandas as pd import numpy as np x = {'Value': ['Test', 'XXX123', 'XXX456', 'Test']} df = pd.DataFrame(x) I want to replace the values starting with XXX with np.nan using lambda. I have tried many things with replace, apply and map and the best I have been able to do is False, True, True, False. The below works, but I would like to know a better way to do it and I think the apply, replace and a lambda is probably a better way to do it. df.Value.loc[df.Value.str

问题 I have a DataFrame: import pandas as pd import numpy as np x = {'Value': ['Test', 'XXX123', 'XXX456', 'Test']} df = pd.DataFrame(x) I want to replace the values starting with XXX with np.nan using lambda. I have tried many things with replace, apply and map and the best I have been able to do is False, True, True, False. The below works, but I would like to know a better way to do it and I think the apply, replace and a lambda is probably a better way to do it. df.Value.loc[df.Value.str

问题 I have a DataFrame: import pandas as pd import numpy as np x = {'Value': ['Test', 'XXX123', 'XXX456', 'Test']} df = pd.DataFrame(x) I want to replace the values starting with XXX with np.nan using lambda. I have tried many things with replace, apply and map and the best I have been able to do is False, True, True, False. The below works, but I would like to know a better way to do it and I think the apply, replace and a lambda is probably a better way to do it. df.Value.loc[df.Value.str

问题 Note: this is a bonus for homework, but I have spent way too long on trying things to no avail. Help is much appreciated, but not necessary I suppose. Premise: generate a powerset for a list of numbers, but without using any helpers, explicit recursion, looping, or functions/constants other than cons , first , rest , empty? , empty , else , lambda , and cond , while using only one define on the language level Intermediate Student with Lambda . The order of the powerset does not matter. What I

问题 Note: this is a bonus for homework, but I have spent way too long on trying things to no avail. Help is much appreciated, but not necessary I suppose. Premise: generate a powerset for a list of numbers, but without using any helpers, explicit recursion, looping, or functions/constants other than cons , first , rest , empty? , empty , else , lambda , and cond , while using only one define on the language level Intermediate Student with Lambda . The order of the powerset does not matter. What I

问题 I'm trying to obtain a better performance in my program by using async whenever this is convenient. My program compiles, but I get the following error every time I use a function containing async calls: C++ exception with description "No associated state" The way I am trying to call async with a lambda is e.g. as follows: auto f = [this](const Cursor& c){ return this->getAbsIndex(c); }; auto nodeAbsIndex = std::async(f,node); // node is const Cursor& auto otherAbsIndex = std::async(f,other);

问题 Let's suppose I have the following task: var task = _entityManager.UseRepositoryAsync(async (repo) => { IEnumerable<Entity> found = //... Get from repository return new { Data = found.ToList() }; } What is the type of task ? Actually, it turns out to be: System.Threading.Tasks.Task<'a> , where 'a is anonymous type: { List<object> Data } How can I explicitly state this type without using var ? I have tried Task<a'> task = ... or Task<object> task = ... but can't manage it to compile. Why do I

问题 Note: This is kind of homework, kind of not -- the end goal is to have a function that produces a powerset of a set of numbers supplied to the function as a list of numbers. I have a recursive version of the function but I now need to find some ways of replacing each explicitly recursive function in the solution I have ( append , mapm etc.) with an equivalent lambda-only expression. As such, I am starting with smaller problems and hope to combine them all to write a full function. I've

问题 Note: This is kind of homework, kind of not -- the end goal is to have a function that produces a powerset of a set of numbers supplied to the function as a list of numbers. I have a recursive version of the function but I now need to find some ways of replacing each explicitly recursive function in the solution I have ( append , mapm etc.) with an equivalent lambda-only expression. As such, I am starting with smaller problems and hope to combine them all to write a full function. I've

问题 This question already has answers here : Pandas conditional creation of a series/dataframe column (8 answers) Closed 2 years ago . I have a DataFrame: A B 1: 0 1 2: 0 0 3: 1 1 4: 0 1 5: 1 0 I want to update each item column A of the DataFrame with values of column B if value from column A equals 0. DataFrame I want to get: A B 1: 1 1 2: 0 0 3: 1 1 4: 1 1 5: 1 0 I've already tried this code df['A'] = df['B'].apply(lambda x: x if df['A'] == 0 else df['A']) It raise an error : The truth value of