PythonTipsandTraps(一)

1. If you want to get the index and content of a list, you can quickly achieve it through enumerate

drinks = ['coffee','tea', 'milk', 'water']for index, drink in enumerate(drinks): PRint ( 'Item {} is {}'.format(index, drink))#Result# Item 0 is coffee# Item 1 is tea# Item 2 is milk# Item 3 is water

2. Set in Python is a An unordered set of non-repeating elements can be very convenient for relationship testing and elimination of duplicate elements

# deduplicate a list fastprint (set(['ham', 'eggs','bacon','ham']))# Result# {'ham', 'eggs', 'bacon'}
# compare list to find difference/similarities # {} without "key":"value" pairs makes a setmenu = {'pancakes', 'ham', 'eggs' , 'bacon'}
new_menu = {'coffee', 'ham', 'eggs', 'bagels', 'bacon'}

new_items = new_menu.difference(menu)print ('try our new', ', ' .join(new_items))# Result: try our new coffee, bagelsdiscontinued_items = menu.difference(new_menu)print ('sorry, we no longer have', ', '.join(discontinued_items))# Result: sorry, we no longer have panckes
old_items = new_menu.intersection(menu)print ('Or get the same old', ', '.join(old_items))# Result: Or ger the same old eggs, ham, baconfull_menu = new_menu.union(menu) print ('At one time or another, we have served ', ','.join(full_menu))

3. namedtuple Generate a tuple subclass that can use names to access element content, very convenient

import collectionshttp:
LightObject = collections.namedtuple('LightObject', ['shortname', 'otherprop'])
n = LightObject(shortname = 'something', otherprop = 'something else')
n.shortname # something

4, deque The biggest advantage of the double-segment queue is that you can add and delete objects from the head popleft(), appendleft()

import collections
d = collections.deque('123456')print d.popleft() # '1'd.appendleft ('7')print d # deque(['7','2','3','4','5','6'])

5. Counter is also in collections and is mainly used To count

import collections
c = collections.Counter('abcab')print c #Couner({'a':2,'b':2,'c':1}

elements method returns an iterator , will generate all elements known by Counter; most_common(n) generates a sequence, including the most commonly used input values ​​​​and corresponding counts

The above is the content of PythonTipsandTraps(1), for more related content, please pay attention to the PHP Chinese website (www.php .cn)!