Python--如何组织项目

Very bad

[...]
from modu import *
[...]
x = sqrt(4)  # Is sqrt part of modu? A builtin? Defined above?
Better

from modu import sqrt
[...]
x = sqrt(4)  # sqrt may be part of modu, if not redefined in between
Best

import modu
[...]
x = modu.sqrt(4)  # sqrt is visibly part of modu's namespace

Bad

# create a concatenated string from 0 to 19 (e.g. "012..1819")
nums = ""
for n in range(20):
  nums += str(n)   # slow and inefficient
print nums
Good

# create a concatenated string from 0 to 19 (e.g. "012..1819")
nums = []
for n in range(20):
  nums.append(str(n))
print "".join(nums)  # much more efficient
Best

# create a concatenated string from 0 to 19 (e.g. "012..1819")
nums = [str(n) for n in range(20)]
print "".join(nums)

foo = 'foo'
bar = 'bar'

foobar = foo + bar  # This is good
foo += 'ooo'  # This is bad, instead you should do:
foo = ''.join([foo, 'ooo'])

Note:

You can also use the % formatting operator to concatenate a pre-determined number

of strings besides str.join() and +. However, according to PEP 3101, the % operator became

deprecated in Python 3.1 and will be replaced by the str.format() method in the later versions.

foo = 'foo'
bar = 'bar'
foobar = '%s%s' % (foo, bar) # It is OK
foobar = '{0}{1}'.format(foo, bar) # It is better
foobar = '{foo}{bar}'.format(foo=foo, bar=bar) # It is best