Python List-Generated

1.1   List-generated

Python's built-in , very simple but powerful build that can be used to create lists .

to generate [1x1, 2x2, 3x3, ..., 10x10] What to do

>>> L = []

>>> for I in range (1, 6):-- Loop

... L.append (i * i)

...

>>> L

[1, 4, 9, 16, 25]

>>> [x * xfor x in range (1, 6)] -- list Generation

[1, 4, 9, 16, 25]

X * x the element to be generated is placed in front and can be followed by an if statement

>>> [x * xfor x in range (1, 6) if x% 2 = = 0]

[4, 16]

Two layers of loops, creating a full array

>>> [M + nfor m in ' ABC ' for n ' XYZ ']

[' AX ', ' AY ', ' AZ ', ' BX ', ' by ', ' BZ ', ' CX ', ' CY ', ' CZ ']

column all files and directories in the current directory

>>> Import OS

>>> [D for D inos.listdir ('. ')] -- found hidden files are listed as well.

['. TCSHRC ', '. DMRC ', ' Desktop ', '. gconf ', '. Redhat ', '. Gnome2_private ', '. BASHRC ', ' python-3.5.0b4 ', '. Python_history ' , ' Redis ', '. CSHRC ', '. Gtkrc-1.2-gnome2 ', ' python ', '. Chewing ', '. Trash ', '. Gnome ', '. Nautilus ', '. KDE ', '. Scim ', '. Lesshst ', '. Bash_logout ', ' python-3.5.0b4.tgz ', '. Gconfd ', '. Xsession-errors ', '. Bash_profile ', '. Xauthority ', '. Gnome2 ', '. Iceauthority ', '. Metacity ', '. gstreamer-0.10 ', '. Bash_history ', '. Eggcups ', '. Mysql_history ', ' shell '

Dict The list-generated

>>> d = {' X ': ' A ', ' y ': ' B ', ' z ': ' C '}

>>> [k + ' = ' + V for K, V in D.items ()]- dict key,value simultaneous iterations, is not very similar

[' Y=b ', ' x=a ', ' z=c ']

>>> L = [' Hello ', ' World ', ' IBM ', ' Apple ']

>>> [s.lower ()for S in L]

[' Hello ', ' World ', ' IBM ', ' Apple ']

Practice Section

because L contains integers and None, and cannot be used only with the lower function.

>>> L = [' Hello ', ' World ', ' Apple ', None]

>>> l_r = []

>>> Len (L)

5

>>> for I in L:

... if Isinstance (I,STR):

... l_r.append (I.lower ())

.. else:

..... l_r.append (i)

...

>>> L_r

[' Hello ', ' world ', ' apple ', None]

This article is from the "90SirDB" blog, be sure to keep this source http://90sirdb.blog.51cto.com/8713279/1796120

Python List-Generated