section 4: Python syntax, you can see the semicolor, and indentation.
if 5 > 2 :
print("Five is greater than two!")
section 10: Python Lists, the main data structure
thislist = ["apple", "banana", "cherry"]
print(thislist)
section 11: Python tuples, not mutable
thistuple = ("apple", "banana", "cherry")
print(thistuple)
note: If you get the result set from a database table
- It is a list with many tuple elements.
- Python language itself does not have type data frame.
- But, its package pandas has type dataframe.
- Package pandas also provides functions to manipulate a dataframe.
- Package pandas also provides data virtualizations(ploting graphics) like R langauge environment.
- This demonstrates that Python can do some special tasks.
the folder structure as below:
folder: lab_subdir
folder: mydir
file: myMath.py
file: main.py
1. create a root folder, lab_standard_module
2. under it, create a text file.
3. under it, create main.py as below:
import os
if os.path.exists("demofile.txt"):
print("It exist.")
else:
print("It does not exist.")
print("os is " + str(type(os)))
print("os.path is " + str(type(os.path)))
4. run it
5. The result is as below:
It exists.
os is 'module'
ps.path is 'dictionary'
os is a standard module. When python3 is installed, it is part
of python installation. There is no need to download when using it.
This demo references w3c python tutorial, file handling.
1. create a root folder, lab_1_web
2. open code visual studio, open the above folder
2. under it, create a python file main.py
3. under it, crete a subfolder, mydir
4. under lab_1_web/mydir, create camelcase_lab.py
----- camelcase_lab.py
import camelcase
c = camelcase.CamelCase()
txt = "merry christmas"
print(c.hump(txt))
print("camelcase is " + str(camelcase))
print("c is " + str(c))
5. no test in code visual studio
6. Following topic 05, open a browser
7. navigate to https://repl.it/site/languages/python3
8. upload the folder mydircreated in step 1-4
9. main.py, code as below
----- main.py ----------------------
#rom mydir import x
from mydir import camelcase_lab
#rom mydir import y
#rom mydir import z
10. on the left, click package icon,
enter camelcase
select it
11. run it.
12. You see
merry christmas => Merry Christmas
camelcase is a module
c is an object.
# mysql_peter.py
import mysql.connector
mydb = mysql.connector.connect(
host="xxxx.winhost.com",
user="xxxxxxxx",
password="xxxxxxxx",
database="mysql_56314_peter"
)
print(mydb)
mycursor = mydb.cursor()
mycursor.execute("SELECT * FROM dogs")
myresult = mycursor.fetchall()
for x in myresult:
print(x)
print(type(myresult)) # list
#('Tairo', 'brown') tuple
#('emi'), 'white').... tuple
print("after mysql test 4")
import pymongo
myclient = pymongo.MongoClient("mongodb://xyz/")
mydb = myclient["mydatabase"]
mycol = mydb["customers"]
myquery = { "address": "Park Lane 38" }
mydoc = mycol.find(myquery)
for x in mydoc:
print(x)
from http.server import HTTPServer, BaseHTTPRequestHandler
print("location 1, test 3")
class Serv(BaseHTTPRequestHandler):
def do_GET(self):
if self.path == '/':
self.path = '/index.html'
try:
file_to_open = open(self.path[1:]).read()
self.send_response(200)
except:
file_to_open = "File not found"
self.send_response(404)
self.end_headers()
self.wfile.write(bytes(file_to_open, 'utf-8'))
print("location 2")
httpd = HTTPServer(('localhost', 8080), Serv)
httpd.serve_forever()
# using constructor functions for casting
# examples as below
y = int(2.8) # y will be 2
w = float("4.2") # w will be 4.2
z = str(3.0) # z will be '3.0'
# in python single quote and double quotes are the same for a string.
| name | assignment | constructor | features |
|---|---|---|---|
| List | l = ["apple", "banana", "cherry"] | l = list(("apple", "banana", "cherry")) | mutable |
| Tuple | t = ("apple", "banana", "cherry") | t = tuple(("apple", "banana", "cherry")) | not mutable |
| Set | s = {"apple", "banana", "cherry"} | s = set(("apple", "banana", "cherry")) | unique contents |
| Dictionary | d = {"brand": "x","model": "y"} | d = dict(brand="x", model="y") | key-value pair |
ref: my topic 30 - 05
#------------ lab 1: lambda function definition -------------------
x = lambda a, b, c : a + b + c
print(x(5, 6, 2)) # 13
print("x is " + str(type(x))) # x is a function
#------------ lab 2: A function using a lambda function -----------------
def myfunc(n): # myfunc is a function
return lambda a : a * n # lambda a : a * n is a function
mydoubler = myfunc(2) # mydoubler is a fimction
print(mydoubler(11))
class Person: # declare a class
#self is needed within the class definition.
def __init__(self, name, age): # used when instantiating an object
self.name = name
self.age = age
def myfunc(self):
print("Hello my name is " + self.name)
p1 = Person("John", 36) # instantiate an object
print(Person) # class _ _ main_ _.Person
print(p1) # _ _ main_ _.Person object at 0x10fe..fo
print(p1.name) # property
p1.myfunc() # method
# --- mymodule.py ---------------
def greeting(name):
print("Hello, " + name)
person1 = {
"name": "John",
"age": 36,
"country": "Norway"
}
# --- test1.py ------------------
import mymodule as mm
mm.person1["age"]) # 36
print(mm.greeting("Mary")) # Hello, Mary
# --- test2.py ------------------
from mymodule import person1
from mymodule import greeting
print(person1["age"]) # Use the dictionary data directly.
greeting("Mary") # Use the function directly.
import platform
x = platform.system()
print(x) # Darvin
A date in Python is not a data type of its own, but we can import a module named datetime to work with dates as date objects.
import datetime #built-in module
print("datetime is " + str(type(datetime))) #module
# lab 1: now()
x = datetime.datetime.now() # create datetime object
print("datetime.datetime is " + str(type(datetime.datetime))) #type
print(type(datetime.datetime.now)) # function or method
print(x) #2018-12-15 18:02:46.402374
print(type(x)) #an object with type datetime.datetime
print(x.year) #2018, its property
# lab 2: creating datetime object
y = datetime.datetime(2020, 5, 17) # This is an Date object
print(y) # 2020-05-17 00:00:00
# lab 3: The datetime object has a method, strftime()
# for formatting date objects into readable strings,
# taking one parameter, format,specifying which part of data you want.
print(x.strftime("%A")) # Saturday %A for weekday
# ---- Convert from JSON to Python: --------------------------
import json # built-in module
print("type of json is " + str(type(json))) # module
# some JSON: the json data wrapped with single quotes
x = '{ "name":"John", "age":30, "city":"New York"}'
# parse x:
y = json.loads(x)
# the result is a Python dictionary:
print(y["age"]) # 30
# ---- Convert a Python object containing all the legal data types: ----
import json
x = {
"name": "John",
"age": 30,
"married": True,
"divorced": False,
"children": ("Ann","Billy"), # python tuple
"pets": None,
"cars": [ # python list
{"model": "BMW 230", "mpg": 27.5}, # python dictionary
{"model": "Ford Edge", "mpg": 24.1} # python dictionary
]
}
# use four indents to make it easier to read the result:
print(json.dumps(x, indent=4)) # a formatted string
x is the json data wrapped with single quotes as a string.
{
"name": "John",
"age": 30, ...
"children": [ #json array
"Ann", string element
"Billy" string element
],
"pets": null,
"cars": [ #json array
{
"model": "BMW 230", key-value pair
"mpg": 27.5 key-value pair
},
...
]
}
# demo 1 ----------------------------------------------------
import re
#Check if the string starts with "The" and ends with "Spain":
txt = "The rain in Spain"
x = re.search("^The.*Spain$", txt)
if (x):
print("YES! We have a match!") # YES...
else:
print("No match")
# demo 2 ----------------------------------------------------
import re
str = "hello world"
x = re.search("\s", str)
if (x):
print("find it")
else:
print("not find it")
# demo 3 ----------------------------------------------------
import re
str = "The rain in Spain"
x = re.findall("[arn]", str)
print(x) # ['r', 'a', 'n', 'n', 'a', 'n']