小数点后第二位停止平均值

Question

I got this code to work but I wanted to get the part I print out to stop at the after 2 numbers after the decimal point (0.00) I don't know how to go about doing this could anyone give some insight of what command I would use to do this. This is the code

import csv

#turn csv files into a list of lists
with open('train.csv','rU') as csvfile:
     reader = csv.reader(csvfile)
     csv_data = list(reader)
with open ('train.csv', 'r') as f:
    numline = len(f.readlines())

# Create two lists to handle the patients
# And two more lists to collect the 'sum' of the columns
# The one that needs to hold the sum 'must' have 0 so we 
# can work with them more easily
iList = []
iList_sum = [0,0,0,0,0,0,0,0,0,0,0,0,0]
IPcounter = 0
hList = []
hList_sum = [0,0,0,0,0,0,0,0,0,0,0,0,0]
HPcounter = 0

# Only use one loop to make the process mega faster
for row in csv_data:
    # If row 13 is greater than 0, then place them as unhealthy
    if (row and int(row[13]) > 0):
        # This appends the whole 'line'/'row' for storing :)
        # That's what you want (instead of saving only one cell at a time)
        iList.append(row)
        IPcounter += 1

    # If it failed the initial condition (greater than 0), then row 13
    # is either less than or equal to 0. That's simply the logical outcome
    else:
        hList.append(row)
        HPcounter += 1


# Loop through all the 'rows' of the ill patient 
for ill_data in iList:

    # Loop through the data within each row, and sum them up
    qmark_counter = 0
    for i in range(0,len(ill_data) - 1):
        if ill_data[i] == '?':
            val = 0

        else:
            val = ill_data[i]
        iList_sum[i] += float(val)



# Now repeat the process for healthy patient
# Loop through all the 'rows' of the healthy patient 
for healthy_data in hList:

    # Loop through the data within each row, and sum them up
    for i in range(0,len(healthy_data) - 1):
        hList_sum[i] += float(ill_data[i])


ill_avg = [ ill / len(iList) for ill in iList_sum]
hlt_avg = [ hlt / len(hList) for hlt in hList_sum]



print('Total number of lines ' + str(numline))
print("Total amount of healthy patients " + str(HPcounter))
print("Total amount of ill patients " + str(IPcounter))
print("Averages of healthy patients " + str(hlt_avg))
print("Averages of ill patients " + str(ill_avg))

This is the output

    Total number of lines 303
Total amount of healthy patients 164
Total amount of ill patients 139
Averages of healthy patients [57.0, 0.0, 2.0, 130.0, 236.0, 0.0, 2.0, 174.0, 0.0, 0.0, 2.0, 1.0, 3.0]
Averages of ill patients [56.62589928057554, 0.8201438848920863, 3.5899280575539567, 134.568345323741, 251.4748201438849, 0.15827338129496402, 1.1726618705035972, 139.25899280575538, 0.5467625899280576, 1.5741007194244607, 1.8273381294964028, 1.129496402877698, 5.798561151079137]

Answer 1

You can use round(number, ndigits) where ndigits is the number of decimal places.

For example

>>> number = 32.32434354
>>> round(number, 2)
32.32
>>> round(number, 5)
32.32434

An alternative is using Python's str.format() .

For example

>>> '{:.2f}'.format(number)
'32.32'
>>> '{:.5f}'.format(number)
'32.32434'

Where,

• {} is .format() 's position to insert the number.

• The f specifies the number will be a float .

• The .2 or .5 means to round it to two or five decimal places.

Answer 2

An alternative is to use the string .format method. Documentation for the specifiers is here . The {} designate where a replacement will occur in the string, f says the replacement will be a float, and .2 tells it to only show 2 digits after the decimal.

print('{:.2f}'.format(32.32434))
# Prints 32.32

To print an array of numbers, with each formatted:

num_list = [1.2345, 2.3456, 3.4567, 4.5678]
print('[' + ', '.join(['{:.2f}'.format(number) for number in num_list]) + ']')
# Prints [1.23, 2.35, 3.46, 4.57]