7. Input and Output
'Hello,world,'
repr(s)
"'Hello,world,'"
str(1/7)
'0.14285714285714285'
x = 10 * 3.25
y = 200 * 2000
s = 'The value of x is ' + repr(x) + ', and y is' + repr(y) +'...'
print(s)
The value of x is 32.5, and y is400000...
# The repr() of a string adds string quotes and backslashes:
hello = 'hello, world\n'
hellos = repr(hello)
print(hellos)
'hello, world\n'
# The argument to repr() may be any Python object:
repr((x,y,('spam','egges')))
"(32.5, 400000, ('spam', 'egges'))"
for x in range(1, 11):
print(repr(x).rjust(2),repr(x*x).rjust(3),end=' ')
# Note use of 'and' on previous line
print(repr(x*x*x).rjust(4))
1 1 1
2 4 8
3 9 27
4 16 64
5 25 125
6 36 216
7 49 343
8 64 512
9 81 729
10 100 1000
for x in range(2,22):
print('{0:2d} {1:3d} {2:4d}'.format(x,x*x,x*x*x))
2 4 8
3 9 27
4 16 64
5 25 125
6 36 216
7 49 343
8 64 512
9 81 729
10 100 1000
11 121 1331
12 144 1728
13 169 2197
14 196 2744
15 225 3375
16 256 4096
17 289 4913
18 324 5832
19 361 6859
20 400 8000
21 441 9261
菜鳥教程網(wǎng)址: "www.runoob.com!"
print('{0}和{1}'.format('Google','Runoob'))
Google和Runoob
print('{1}和{0}'.format('Google','Runoob'))
Runoob和Google
print('{name}網(wǎng)址: {site}'.format(name='菜鳥教程',site='www.henrytien.com'))
菜鳥教程網(wǎng)址: www.henrytien.com
print('站點列表 {0},{1},和{other}.'.format('Google','Runoob',other='Taobao'))
站點列表 Google,Runoob,和Taobao.
print('My hovercraft is full of {}.'.format(conttens))
My hovercraft is full of eels.
print('My hovercraft if full of {!r}.'.format(conttens))
My hovercraft if full of 'eels'.
print('The value ofPI is approximately {0:.3f}.'.format(math.pi))
The value ofPI is approximately 3.142.
table = {'Google':1,'Runoob':2,'Taobao':3}
for name, number in table.items():
print('{0:10} ==> {1:10d}'.format(name,number))
Google ==> 1
Runoob ==> 2
Taobao ==> 3
7.2 Reading and Writing Files
f = open("C:/Users\henry\desktop/foo.txt",'rb+')
f.write(b'lsldllsas')
9
f.seek(5)
5
f.read(1)
b'l'
f.seek(-3,2)
27
f.read(1)
b'1'
7.2.2. Saving strucured data with json
import json
json.dumps([1,'simple','list'])
'[1, "simple", "list"]'
json.dump(x,f)