introduction

print(2+3*4) print((2+3)*4) print(2**10) print(6/3) print(7/3) print(7//3) print(7%3) print(3/6) print(3//6) print(3%6) print(2**100)

output
14 20 1024 2.0 2.33333333333 2 1 0.5 0 3 1267650600228229401496703205376

• 注意：3/6=0.5 3//6=0

• 逻辑运算符：and or not

2.list

Note that the indices for lists (sequences) start counting with** 0**. The slice operation, myList[1:3], returns a list of items starting with the item indexed by 1 up to but not including the item indexed by 3.

下标从0开始，切片时为左闭右开

myList = [1,2,3,4] A = [myList]*3 print(A) myList[2]=45 print(A)
A:
[[1,2,45,4],[1,2,45,4],[1,2,45,4]]
** 注意 ：** 列表的重复，是引用的对象的重复，如果引用的对象发生了改变，则重复后的list也发生了变化。

The variable A holds a collection of three references to the original list called myList. Note that a change to one element of myList shows up in all three occurrences in A.

Paste_Image.png

• range,左闭右开

>>> range(10)
range(0, 10)
>>> list(range(10))
[0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
>>> range(5,10)
range(5, 10)
>>> list(range(5,10))
[5, 6, 7, 8, 9]
>>> list(range(5,10,2))
[5, 7, 9]
>>> list(range(10,1,-1))
[10, 9, 8, 7, 6, 5, 4, 3, 2]

• string

>>> myName
'David'
>>> myName.upper()
'DAVID'
>>> myName.center(10)
'  David   '
>>> myName.find('v')
2
>>> myName.split('v')
['Da', 'id']

• list与string之间的区别：list可以被改变，string不可以．
• tuple与list很相似，但是tuple不可变，list可变

3.set

>>> mySet
{False, 4.5, 3, 6, 'cat'}
>>> yourSet = {99,3,100}
>>> mySet.union(yourSet)
{False, 4.5, 3, 100, 6, 'cat', 99}
>>> mySet | yourSet
{False, 4.5, 3, 100, 6, 'cat', 99}
>>> mySet.intersection(yourSet)
{3}
>>> mySet & yourSet
{3}
>>> mySet.difference(yourSet)
{False, 4.5, 6, 'cat'}
>>> mySet - yourSet
{False, 4.5, 6, 'cat'}
>>> {3,100}.issubset(yourSet)
True
>>> {3,100}<=yourSet
True
>>> mySet.add("house")
>>> mySet
{False, 4.5, 3, 6, 'house', 'cat'}
>>> mySet.remove(4.5)
>>> mySet
{False, 3, 6, 'house', 'cat'}
>>> mySet.pop()
False
>>> mySet
{3, 6, 'house', 'cat'}
>>> mySet.clear()
>>> mySet
set()
>>>

4.dict

５input and output

aName = input('Please enter your name: ')

output:

>>> print("Hello")
Hello
>>> print("Hello","World")
Hello World
>>> print("Hello","World", sep="***")
Hello***World
>>> print("Hello","World", end="***")
Hello World***>>>

print(aName, "is", age, "years old.")
print("%s is %d years old." % (aName, age))

>>> price = 24
>>> item = "banana"
>>> print("The %s costs %d cents"%(item,price))
The banana costs 24 cents
>>> print("The %+10s costs %5.2f cents"%(item,price))
The     banana costs 24.00 cents
>>> print("The %+10s costs %10.2f cents"%(item,price))
The     banana costs      24.00 cents
>>> itemdict = {"item":"banana","cost":24}
>>> print("The %(item)s costs %(cost)7.1f cents"%itemdict)
The banana costs    24.0 cents
>>>