Python（v2.7）格式和打印

Question

I'm trying to figure out how to print and format the 1st two rows a list that was read in as a csv file and converted to floating point data (Python v2.7). Data was then normalized. I can print out the rows by using a separate print line for each row, but I cant figure out how to only display say the first 3 places after the decimal point.

Depending on what I try I sometimes get error message of : Unknown format code 'f' for object of type 'str' - but the data was converted to floating point - so I don't understand message.

Any tips on how to get the first 2 rows printed and formatted ? I have tried looking through here https://docs.python.org/2/tutorial/datastructures.html#list-comprehensions , but couldn't solve anything.

# Normalize columns
normalize_dataset(dataset, minmax)
print ('1st row after normalization', dataset[0])
print ('2nd row after normalization', dataset[1])
#for row in range(2):
 #   print dataset
[format(row, '.3f') for row in dataset]
#print ("Normalization", format(dataset, '.3f'))

Attached is the output when I just print two rows with no formatting using a separate line for each row. output

Updated with code I am using to convert string to float:

    for i in range(len(dataset[0])):
        str_to_float(dataset, i) 

    def str_to_float(dataset, column):
        for row in dataset:
        row[column] = float(row[column].strip())

Answer 1

为此使用.format方法。

print("{0:.2f}".format(dataset))