List describes
Think about it:
String in front of a bunch of learning can be used to store information, then think about how to store the names of all the students in our class do?
Define 100 variables, each store a student's name can you? There is a better way?
A: List
Format list: A type of variable as a list
namesList = [ 'xiaoWang', 'xiaoZhang', 'xiaoHua']
C than an array of powerful local language that elements in the list can be different types of
testList = [1,'a']
Print List:
demo:
namesList = ['xiaoWang', 'xiaoZhang', 'xiaoHua']
print(namesList[0])
print(namesList[1])
print(namesList[2])
result:
xiaowang
Xiaozhang
xiaohua
Loop through the list of
1. Use a for loop
For each data output list of more efficient, can be accomplished using a loop
demo：
namesList = ['xiaoWang', 'xiaoZhang', 'xiaoHua']
for name in namesList:
print(name)
result:
xiaowang
Xiaozhang
xiaohua
2. Use a while loop
For each data output list of more efficient, can be accomplished using a loop
demo：
namesList = ['xiaoWang', 'xiaoZhang', 'xiaoHua']
length = len(namesList)
i = 0
while i < length:
print(namesList[i])
i += 1
result:
xiaowang
Xiaozhang
xiaohua
List of related operations
Data is stored in the list can be modified, such as "add", "delete", "change", "check"
<1> additive element ( "increase" append, extend, insert)
append: you can add elements to the list (tail) by append
demo：
result:
extend: one by one can add another set of the elements extend through to the list
demo：
result:
append and extend the difference?
append demo： extend demo：
Results: The results:
insert: insert (index, object) prior to the specified object access element location index
demo：
result:
<2> modified element ( "change")
Modify elements of time, to determine which element is to be modified by the subscript, and then to make changes
demo：
result:
<3> Find elements (check in, not in, index, count)
The so-called lookup, is to look at the specified element exists
in，not in
Python find common method of:
in (there is): If there is then the result is True, otherwise False
not in (does not exist): If there is then the result is True, or False
demo：
result:
Description:
The method will be used in long, then the same is not in use, but not in judgment does not exist
not in
demo：
result:
index，count
index and count with the use of the same string! ! !
demo：
result:
<4> Remove elements ( "delete" del, pop, remove)
In real life analogy, if a student transfer classes, then it should be left to the transfer student's name removed, often used in the development of this function deleted
Common delete method list elements are:
- del: delete according to index
- pop: Removes the last element (also may be deleted as subscript)
- remove: remove as value elements
demo (the)
result:
demo：（pop）
result:
demo：（remove）
result:
<5> sorted (sort, reverse)
sort the list is rearranged in a specific order, the default is small to large, reverse = True parameters can be changed to reverse, descending
reverse method is to list Retrograde
demo：
result:
Nested list
Similar nested while loop, also supports nested list, a list is a list of the elements, then this is a nested list
schoolNames = [[ 'Peking', 'Tsinghua University'], [ 'Nankai', 'Tianjin University', 'Tianjin Normal'], [ 'Zhejiang University'], [ 'Hebei University', 'Hebei University of Science and Technology ']]
demo：
result:
