How to convert MB to GB with precision in Python

Question

What would be the fastest way to covert the values given in MB and KB to GB and TB?

sizes = ['999.992 MB', '2.488 GB', '401 KB']

sizes_in_GB = ['?', '?', '?']

sizes_in_TB = ['?', '?', '?']

Answer 1

Given:

>>> sizes = ['999.992 MB', '2.488 GB', '401 KB']

First agree on what 'precision' means. Since your input is a float, it is a fair assumption that 'precision' is limited to the input precision.

To calculate, first convert to base bytes (know though that your actual precision is no better than the input precision):

>>> defs={'KB':1024, 'MB':1024**2, 'GB':1024**3, 'TB':1024**4} 
>>> bytes=[float(lh)*defs[rh] for lh, rh in [e.split() for e in sizes]]
>>> bytes
[1048567611.392, 2671469658.112, 410624.0]

Then convert to magnitude desired:

>>> sd='GB'
>>> ['{:0.2} {}'.format(e/defs[sd], sd) for e in bytes]
['0.98 GB', '2.5 GB', '0.00038 GB']
>>> sd='MB'
>>> ['{:0.2} {}'.format(e/defs[sd], sd) for e in bytes]
['1e+03 MB', '2.5e+03 MB', '0.39 MB']
>>> sd='TB'
>>> ['{:0.2} {}'.format(e/defs[sd], sd) for e in bytes]
['0.00095 TB', '0.0024 TB', '3.7e-07 TB']

Answer 2

Heres something I found online.

def conv_KB_to_MB(input_kilobyte):
        megabyte = 1./1000
        convert_mb = megabyte * input_kilobyte
        return convert_mb
def conv_MB_to_GB(input_megabyte):
        gigabyte = 1.0/1024
        convert_gb = gigabyte * input_megabyte
        return convert_gb
#Create the menu


print "Enter 1 to convert from KBs to MBs"
print "Enter 2 to convert from MBs to GBs"


try:
        menu_choice = (raw_input("Enter a selection"))
except ValueError:
        print "This is not a number"
except NameError:
        print "Name Error"
except SystenError:
        print "Syntax Error"

if menu_choice == '1':
        kb_input = float(input("Enter KBs"))
        megabytes = conv_KB_to_MB(kb_input)
        print megabytes

elif menu_choice == '2':
        mb_input = float(input("Enter MBs"))
        gigabytes = conv_MB_to_GB(mb_input)
        print gigabytes
else:
        print "exiting"

Source:http://www.sfentona.net/?p=1965