一、slicing
# 最后3个元素
>>> a[-3:]
# 除了最后2个元素
>>> a[:,-2]
二、list comprehension
>>> [expression for object in iterable if condition]
>>> [[j,k] for j in range(4) for k in range(4) if j < k]
>>> [s for s in ['aa', ''bb', 'cc'] if 'a' in s]
三、file
file("data.txt", "r").read() #返回string
file("data.txt", "r").readlines() #返回list
readlines() = read().split('\n')
# gzip 压缩文件
import gzip
f = gzip.GzipFile("data.txt", "w")
f.write("This is a test for compression.")
f.close()
print gzip.GzipFile("data.txt", "r").read()
四、path
# 生成路径
>>> p = os.path.join("c:\", "temp", "file.txt")
>>> os.path.exists(p)
>>> os.path.isfile(p)
>>> os.path.isdir(p)
>>> os.path.getsize(p)
>>> os.getcwd()
>>> os.chdir("..")
>>> os.mkdir("c:/temp/newdir") # create a dir
>>> os.remove("c:/temp/deleteme.txt") # delete a file
>>> os.rmdir("c:/temp/newdir") # delete a dir
>>> os.rename("c:/temp/file.txt, "c:/temp/newname.txt") # rename a file
# import shutil # copy和move文件
# import glob # 找文件名
五、time
>>> import time
>>> time.time() # 返回seconds
t1 = time.time()
ComputerEnergies()
t2 = time.time()
print("The time required was %.2f sec" % (t2-t1))
# 更简洁的写法
import cProfile
cProfile.run("ComputeEngergies()")
