Question :
I read that I can use Python’s Format Specification Mini-Language to have more control over how strings are displayed. However, I am having a hard time figuring out how to use it to display floats aligned on the decimal point.
For example, say I have thre following three lists:
job_IDs = ['13453', '123', '563456'];
memory_used = [30, 150.54, 20.6];
memory_units = ['MB', 'GB', 'MB'];
I would like to iterate through these three lists and print
Job 13453: 30 MB
Job 123: 150.54 MB
Job 563456: 20.6 GB
So far I have tried:
for i in range(len(jobIDs)):
my_str = "{item:15}{value:6} {units:3}".format(
item='Job ' + job_IDs[i] + ':' , value=str(memories[i]),units=memory_units[i]);
print my_str
which prints:
Job 13453: 30 MB
Job 123: 150.54 MB
Job 563456: 20.6 GB
which is almost right, but it does not align the floats around the decimal point. How can I use Python’s Format Specification Mini-Language to do it the way I need?
Answer #1:
This is what you want:
for i in range(len(job_IDs)):
print "Job {item:15} {value[0]:>6}.{value[1]:<6} {units:3}".format(item=job_IDs[i]+':', value=memory_used[i].split('.') if '.' in memory_used[i] else (memory_used[i], '0'), units=memory_units[i])
Here is how it works:
This is the main part: value=memory_used[i].split('.') if '.' in memory_used[i] else (memory_used[i], '0'), which means: if there is a decimal point, split the string as the whole and decimal part, or set the decimal part to 0.
Then in the format string: {value[0]:>6}.{value[1]:<6} means, the whole part shifted right, followed by a dot, then the decimal part shifted left.
which prints:
Job 13453: 30.0 MB
Job 123: 150.54 GB
Job 563456: 20.6 MB
Answer #2:
Here’s another implementation based on .split('.') idea. It might be more readable. Split on '.', right-align the left part, left-align the right part:
width = max(map(len, job_IDs)) # width of "job id" field
for jid, mem, unit in zip(job_IDs, memory_used, memory_units):
print("Job {jid:{width}}: {part[0]:>3}{part[1]:1}{part[2]:<3} {unit:3}".format(
jid=jid, width=width, part=str(mem).partition('.'), unit=unit))
Output
Job 13453 : 30 MB
Job 123 : 150.54 GB
Job 563456: 20.6 MB
Answer #3:
In case it helps, here’s a similar function I use:
def align_decimal(number, left_pad=7, precision=2):
"""Format a number in a way that will align decimal points."""
outer = '{0:>%i}.{1:<%i}' % (left_pad, precision)
inner = '{:.%if}' % (precision,)
return outer.format(*(inner.format(number).split('.')))
It allows a fixed precision after the decimal point.
Answer #4:
This does it:
import re
job_IDs = ['13453', '123', '563456']
memory_used = ['30', '150.54', '20.6']
memory_units = ['MB', 'GB', 'MB']
for i in range(len(job_IDs)):
lh=re.match(r'(d+)',memory_used[i]).group(1)
if '.' in memory_used[i]:
rh=re.match(r'(d+).(d+)',memory_used[i]).group(2)
sep='.'
else:
rh=''
sep=' '
my_str = "{item:15}{l:>6}{s:1}{r:6} {units:3}".format(
item='Job ' + job_IDs[i] + ':' , l=lh,s=sep,r=rh,units=memory_units[i])
print my_str
To get your precise out put, you need to break the strings on the optional ‘.’
You could also convert those strings to floats.
