Python QuickStart
来自Jack's Lab
目录 |
1 Quick Start
- Install python3.8 from https://www.python.org/downloads/
Install pip:
$ curl https://bootstrap.pypa.io/get-pip.py -o get-pip.py $ sudo python get-pip.py
Using the pip to install the numpy and tensorflow package:
$ sudo pip3 install numpy pandas matplotlib $ sudo pip3 install scipy $ sudo pip3 install tensorflow
$ pip3 install --upgrade pip $ pip3 install jupyter
2 Bytes to string
3 Basics
3.1 Numbers
Python 2.7.9 (default, Mar 1 2015, 12:57:24) >>> a = 3.23 >>> b = 4 >>> c = 52.3E-4 >>> print a, b, c 3.23 4 0.00523
3.2 HEX
>>> print str(254) 254 >>> print hex(254) 0xfe >>> print hex(254).upper() 0XFE >>> str = "%02X" %(254); print str FE >>> print hex(1023) 0x3ff >>> print hex(1023)[0:-2] 0x3
3.3 Strings
#!/usr/bin/python
str_1 = 'Jack Tan'
str_2 = "Ga Xiao Duo"
str_3 = '''This is a multi-line string. first line.
second line'''
# using the startswith method of the string object
if str_1.startswith('Ja'):
print("Yes, str_1 start with 'Ja'")
if 'a' in str_1:
print('Yes, str_1 contains the string "a"')
substr = 'ac'
if str_1.find(substr) != -1:
print('Yes, str_1 contains the string "{0}"'.format(substr))
print('Yes, {0} contains the string "{1}"'.format('str_1', substr))
print('Yes, {} contains the string "{}"'.format('str_1', substr))
# using the format method of the string object
deli = '_*_'
mylist = ['Brazil', 'Russia', 'India', 'China']
# using the join method of the string object
print(deli.join(mylist))
Output:
Yes, name start with 'Ja' Yes, name contains the string "a" Yes, name contains the string "ac" Brazil_*_Russia_*_India_*_China
Once your have created a string, you cannot change it
3.4 Variable
Python refers to anything used in a program as an object.
Do not need type declaration of variable in python
Python 2.7.9 (default, Mar 1 2015, 12:57:24) >>> a = 3.1415 >>> b = 100000 >>> c = 'Jack Tan' >>> d = ['x1', 'x2'] >>> print a, b, c, d 3.1415 100000 Jack Tan ['x1', 'x2'].
Variables can hold values of different types called data types. The basic types are numbers and strings. We can create our own types using classes.
3.5 Indentation
Whitespace at the beginning of the line is important!
Spaces and tabs at the beginning of the logical line are used to determine the indentation level of the logical line, which in turn is used to determine the grouping of statements.
Statements which go together must have the same indentation. Each usch set of statements is called a block
3.6 Format
#!/usr/bin/python #width = 10,precise = 3,align = left print "PI = %10.3f" %(math.pi) # don't add the '\n' at the end of line print "PI = %10.3f" %(math.pi), #width = 10,precise = 3,align = rigth print "PI = %-10.3f" % math.pi
Output:
PI = 3.141593 PI = 3.142
Python 2.7.9 (default, Mar 1 2015, 12:57:24)
>>> print "%.3s " % ("jcodeer") #precise = 3
jco
>>> print "%.*s" % (4,"jcodeer") #precise = 4
jcod
>>> print "%10.3s" % ("jcodeer") #width = 10,precise = 3
jco
>>>
fmat = "%r %r %r %r"
print fmat % (1, 2, 3, 4)
print fmat % ("one", "two", "three", "four")
print fmat % (True, False, False, True)
1 2 3 4 'one' 'two' 'three' 'four' True False False True
print('{0:.3}'.format(0.3333333))
#print('{0:.3}'.format(1/3))
print('{0:_^11}'.format('Hello'))
print('{0:+^11}'.format('Hello'))
print('{name} wrote {book}'.format(name='Jack', book='Hello world'))
PI = 3.141593 PI = 3.142 0.333 ___Hello___ +++Hello+++ Jack wrote Hello world
3.7 yield
类 return 作用，不过返回的是生成器，可以用 for ... in generator 或 next 遍历该生成器
4 Operators
5 Control Flow
5.1 if
i = 5
if i == 0:
print 'Zero'
elif i > 0:
print 'Positive'
else:
print 'Negative'
5.2 While
n = 4
while n:
print 'Loop is OK'
n -= 1
else:
print 'Loop is over'
5.3 For
for ... in
for i in range(1,5):
print i
else:
print 'The loop is over'
6 Functions
7 Data Structures
7.1 Dict
7.2 List
中括号 [] 声明
7.3 元组
括号声明，一旦定义 元素不可更改
8 Exceptions
8.1 with...as
#!/usr/bin/python
import sys
class test:
def __enter__(self):
print("enter")
return 1
def __exit__(self, *args):
print("clean up")
return False
#return True
with test() as t:
print("t is not the result of test(), it's __enter__ returned")
print("t is 1, yes, it's {0}".format(t))
print "t is 1, yes, it's", t
raise NameError("Error")
sys.exit()
print("Never here")
9 Matplotlib
- Gallery
- Change the Colors Changes to the default style
- Demo Fixed Size Axes
- Multiple Figs Demo
- Usetex Demo
- Controlling style of text and labels using a dictionary
- matplotlib.pyplot.plot()
- matplotlib.pyplot.figure()
9.1 bar
def currency(x, pos):
"""The two args are the value and tick position"""
if x >= 1e6:
s = '${:1.1f}M'.format(x*1e-6)
else:
s = '${:1.0f}K'.format(x*1e-3)
return s
formatter = FuncFormatter(currency)
fig, ax = plt.subplots(figsize=(6, 8))
ax.xaxis.set_major_formatter(formatter)
9.2 hist
10 Numpy
import numpy as np
import matplotlib.pyplot as plt
ds = np.arange(0,737280, 1, np.uint8)
ds = np.reshape(ds, (1024, 720))
plt.imsave('test.jpg', ds)
11 Seaborn
11.1 Panel
12 Modules
12.1 Serial
import serial
import string
import binascii
s = serial.Serial('com4',9600)
s.open()
# rx data
n = s.inwaiting()
if n:
data = str(binascii.b2a_hex(s.read(n)))[2:-1]
print(data)
# tx data
d = bytes.fromhex('10 11 12 34 3f')
s.write(d)
s.close()
12.2 Struct (TX binary data)
import struct
a = [0x00, 0x00, 0x00, 0x2c, 0x63, 0x00, 0x00, 0x00, 0x75, 0x4b, 0xef, 0x0f]
s = socket.socket(socket.AF_INET,socket.SOCK_STREAM)
s.connect(('127.0.0.1',8000))
date = struct.pack("%dB"%(len(a)),*a)
s.send(date)
12.3 MQTT
Please refer to: http://wiki.jackslab.org/Noduino_OpenPlug#Turn_off_2
12.4 HTTP
httplib 实现了 http & https 的客户端协议，模块 urllib 和 urllib2 对 httplib 进行了更上层的封装
#!/usr/bin/env python
# -*- coding:utf-8 -*-
import urllib2
import json
def http_post(url,data_json):
jdata = json.dumps(data_json)
req = urllib2.Request(url, jdata)
response = urllib2.urlopen(req)
return response.read()
url = 'http://192.168.0.100:8080/dev/test'
data_json = {'data' : '112233'}
resp = http_post(url, data_json)
print(resp)
使用post方式时，数据放在 data 或者 body 中：
import urllib
import urllib2
test_data = {'ServiceCode':'aaaa','b':'bbbbb'}
test_data_urlencode = urllib.urlencode(test_data)
requrl = "http://192.168.1.16/dev/test"
req = urllib2.Request(url = requrl, data =test_data_urlencode)
print req
res_data = urllib2.urlopen(req)
res = res_data.read()
print res
Python3:
import urllib.request as http
resp = http.urlopen('http://iot.xxx.net')
# print(resp.info())
resp.read()
resp.close()
Reference: https://docs.python.org/3.8/library/urllib.request.html#module-urllib.request
13 CSV
import csv
csvfile = open('data-text.csv', 'rb')
reader = csv.reader(csvfile)
for row in reader:
print row
13.1 Time
13.2 PDF
$ pip3 install pdfplumber
Refer to: https://zhuanlan.zhihu.com/p/40221732
import pdfplumber
import pandas as pd
pdf = pdfplumber.open('ncp-who.pdf')
page0 = pdf.pages[0] #PDF 文件的第一页
table = page0.extract_table()
d = pd.DataFrame(table)
print(d.loc[0])
d.to_csv('ncp-who.csv', index = False, header = True, date_format='%Y%m%d')
复杂的，参考：https://github.com/jsvine/pdfplumber/blob/master/examples/notebooks/extract-table-nics.ipynb
14 getopt
14.1 sys
import sys
print(sys.argv[0])
for i in range(1, len(sys.argv)):
print (i, sys.argv[i])
$ python test.py hello world test.py 1 hello 2 world
14.2 getopt
import sys, getopt
opts, args = getopt.getopt(sys.argv[1:], "hi:o:")
input_file=""
output_file=""
for op, value in opts:
if op == "-i":
input_file = value
elif op == "-o":
output_file = value
elif op == "-h":
usage()
sys.exit()
def main(argv):
inputfile = ''
outputfile = ''
try:
opts, args = getopt.getopt(argv,"hi:o:",["ifile=","ofile="])
except getopt.GetoptError:
print ('test.py -i <inputfile> -o <outputfile>')
sys.exit(2)
for opt, arg in opts:
if opt == '-h':
print ('test.py -i <inputfile> -o <outputfile>')
sys.exit()
elif opt in ("-i", "--ifile"):
inputfile = arg
elif opt in ("-o", "--ofile"):
outputfile = arg
print ('Input file is "', inputfile)
print ('Output file is "', outputfile)
if __name__ == "__main__":
main(sys.argv[1:])
15 Resource
- Online Python: http://www.compileonline.com/execute_python_online.php
- Python Quick Start: http://www.tutorialspoint.com/python/python_lists.htm
