如何遍历 CSV 文件并根据另一列的值更新一列中的值

Question

I have a csv file with one column titled 'pages' that is empty for all of the rows of the file. I want to fill in this empty value in each row based on the value of 'size' for that row. For example, if the size is less than 100, then I want the empty value to be replaced with 1, and if the 'size' value is greater than 100, I want the empty value to be replaced with 2. I am doing this in python. I have tried some things like:

data = pd.read_csv("example.csv")         
data["pages"] = ""      
data.to_csv("example.csv", index=False)
for row in data.iterrows(): 
    if row['size']>100:
        data["pages"]= "1" 

but it is not working. I have uploaded an image of what the data may look like. Thank you for your help!

Answer 1

You can use apply method to do it.Try this

data["pages"] = data["size"].apply(lambda x: "2" if x>100 else "1")

Or like this

data["pages"] = (data["size"]>100).map({True: '2', False: '1'})