要求：列出1~10中大于等于4的数字的平方
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1、普通方法：
>>> L = []
>>> for i in range(1,11):
... if i >= 4:
... L.append(i**2)
...
>>> print L
[16, 25, 36, 49, 64, 81, 100]
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2、列表解析
>>>L = [ i**2 for i in range(1,11) if i >= 4 ]
>>>print L
[16, 25, 36, 49, 64, 81, 100]
if判断for循环中满足条件的i 进行 左边i操作
深入
要求：列出"/var/log"中所有已'.log'结尾的文件
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1、普通方法
>>>import os
>>>file = []
>>> for file in os.listdir('/var/log'):
... if file.endswith('.log'):
... file.append(file)
...
>>> print file
['anaconda.ifcfg.log', 'Xorg.0.log', 'anaconda.storage.log', 'Xorg.9.log', 'yum.log', 'anaconda.log', 'dracut.log', 'pm-powersave.log', 'anaconda.yum.log', 'wpa_supplicant.log', 'boot.log', 'spice-vdagent.log', 'anaconda.program.log']
##################################################
2.列表解析
>>> import os
>>> file = [ file for file in os.listdir('/var/log') if file.endswith('.log') ]
>>> print file
['anaconda.ifcfg.log', 'Xorg.0.log', 'anaconda.storage.log', 'Xorg.9.log', 'yum.log', 'anaconda.log', 'dracut.log', 'pm-powersave.log', 'anaconda.yum.log', 'wpa_supplicant.log', 'boot.log', 'spice-vdagent.log', 'anaconda.program.log']
要求：实现两个列表中的元素逐一配对。
1、普通方法:
>>> L1 = ['x','y','z']
>>> L2 = [1,2,3]
>>> L3 = []
>>> for a in L1:
... for b in L2:
... L3.append((a,b))
...
>>> print L3
[('x', 1), ('x', 2), ('x', 3), ('y', 1), ('y', 2), ('y', 3), ('z', 1), ('z', 2), ('z', 3)]
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2、列表解析:
>>> L1 = ['x','y','z']
>>> L2 = [1,2,3]
L3 = [ (a,b) for a in L1 for b in L2 ]
>>> print L3
[('x', 1), ('x', 2), ('x', 3), ('y', 1), ('y', 2), ('y', 3), ('z', 1), ('z', 2), ('z', 3)]
列表解析比使用普通方法的速度几乎可以快1倍
娱乐
print('\n'.join([''.join(['%s*%s=%-2s '%(y,x,x*y)for y in range(1,x+1)])for x in range(1,10)]))
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