我不知道的python （补充）
1.原来swap is easy. Just use a,b=b,a
2.Catch errors rather than avoiding: Use try: except: expression is better
easier to ask forgiveness than permission.
3.Use map, filter expression:
def triple(x):
"""Returns 3 * x.Count: raises AttributeError if .Count missing."""
return 3 * x.Count
def check_count(x):
"""Returns 1 if x.Count exists and is greater than 3, 0 otherwise."""
try:
return x.Count > 3
except:
return 0
result = map(triple, filter(check_count, data))
4.zip('abc', [1,2,3]) == [('a',1),('b',2),('c',3)]
5. Method to do sum,multiply
from operator import add, mul
sum = reduce(add, data)
product = reduce(mul, data)
6. list sort reverse
list.sort()
list.reverse()
7. Use dictionaries (or sets) for searching, not lists. To find items in common between two lists, make the first into a dictionary and then look for items in the second in it.
2.Catch errors rather than avoiding: Use try: except: expression is better
easier to ask forgiveness than permission.
3.Use map, filter expression:
def triple(x):
"""Returns 3 * x.Count: raises AttributeError if .Count missing."""
return 3 * x.Count
def check_count(x):
"""Returns 1 if x.Count exists and is greater than 3, 0 otherwise."""
try:
return x.Count > 3
except:
return 0
result = map(triple, filter(check_count, data))
4.zip('abc', [1,2,3]) == [('a',1),('b',2),('c',3)]
5. Method to do sum,multiply
from operator import add, mul
sum = reduce(add, data)
product = reduce(mul, data)
6. list sort reverse
list.sort()
list.reverse()
7. Use dictionaries (or sets) for searching, not lists. To find items in common between two lists, make the first into a dictionary and then look for items in the second in it.
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