Python: Difference between revisions

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=links=
=version=
http://en.wikibooks.org/wiki/Non-Programmer%27s_Tutorial_for_Python_2.6
Show python version
http://docs.python.org/tutorial
  python -V
Reference
=make an http request=
  http://docs.python.org/ref/ref.html
  import requests
http://docs.python.org/library/
  r =requests.get('https://halfface.se')
 
  print(r.text)
=basics=
=dictionary=
 
  dictionary = {"a": 99, "hello": "world"}
  print "Hello, World!"
command called print followed by one argument,which is "Hello, World!". (referred to as a string of characters, or string) Command and its arguments are collectively referred to as a statement,
 
  print "2 + 2 is", 2 + 2
The first argument is the string "2 + 2 is" and the second argument is the mathematical expression 2 + 2, which is commonly referred to as an expression. each of the arguments separated by a comma
 
sys.argv  arguments are passed to the script in the variable sys.argv
#          is used to start a comment
=operations for numbers=
{| class="wikitable"
! Operation
! Symbol
! Example
|-
|Power (exponentiation)
| <code>**</code>
| <code>5 ** 2 == 25</code>
|-
|Multiplication
| <code>*</code>
|<code>2 * 3 == 6</code>
|-
|Division
| <code>/</code>
| <code>14 / 3 == 4</code>
|-
|Remainder (modulo)
| <code>%</code>
| <code>14 % 3 == 2</code>
|-
|Addition
| <code>+</code>
| <code>1 + 2 == 3</code>
|-
|Subtraction
| <code>-</code>
| <code>4 - 3 == 1</code>
|}
=userinput=
raw_input (returns a string)
user_reply = raw_input("Who goes there? ")
 
input (returns digits)
number = input("Type in a number: ")
type(number) (tells what a variable is.)
  print "number is a", type(number)
=while loop=
print number interval. finish while loop with a ':' The while statement only affects the lines that are indented with whitespace.
start = input("Start number? ")
stop = input("Stop number? ")
a = start
  while a < stop:
    print a
    a = a + 1
{| class="wikitable"
!operator
!function
|-
|<code><</code>
|less than
|-
|<code><=</code>
|less than or equal to
|-
|<code>></code>
|greater than
|-
|<code>>=</code>
|greater than or equal to
|-
|<code>==</code>
|equal
|-
|<code>!=</code>
|not equal
|-
|<code><></code>
|another way to say not equal (old style, not recommended)
|}
 
=if statment=
  if a > 5: 
    print a, ">", 5
  elif a <= 7:
    print a, "<=", 7
  else:
    print "Neither test was true"


# This Program Demonstrates the use of the == operator  # using numbers
print 5 == 6
false
=functions=
The key feature of this program is the def statement. def (short for define) starts a function definition. def is followed by the name of the function absolute_value. Next comes a '(' followed by the parameter n (n is passed from the program into the function when the function is called). The statements after the ':' are executed when the function is used. The statements continue until either the indented statements end or a return is encountered. The return statement returns a value back to the place where the function was called.
def absolute_value(n):
  if n < 0:
    n = -n
  return n
=import=
=import=
command import loads a module
Import functions.
==Sleep==
import $module
import time
=try:=
time.sleep(secs)
Exception handling. Example will fail because x is unset.
==random==
  try:
  import random
  print(x)
number = random.randrange(1, 100, 1)
  except:
==deepcopy===
  print("An exception occurred")
  to copy lists that contain lists use deepcopy
=sys.exit()=
import copy
  exits and no stack traceback is printed.
c = copy.deepcopy(a)
=re=
 
Regular expression searching
==list==
  ip = re.findall(r'[0-9]+(?:\.[0-9]+){3}', config_info)
list with more than one value.
=join elements in list for other output=
which_one = input("What month (1-12)? ")
print(', '.join(configured_ip_addresses))
months = ['January', 'February', 'March', 'April', 'May', 'June', 'July', 'August', 'September', 'October', 'November', 'December']
  if 1 <= which_one <= 12:
  print "The month is", months[which_one - 1]
 
Print a whole list.
demolist = ["life", 42, "the universe", 6, "and", 7]
print "demolist = ",demolist
demolist =  ['life', 42, 'the universe', 6, 'and', 7]
 
  b = a
makes b a reference to a.
b = a * 1
b = a[:]
copies b to a.
 
=operations=
 
{| class="wikitable"
!example
!explanation
|-
|<code>demolist[2]</code>
|accesses the element at index 2
|-
|<code>demolist[2] = 3</code>
|sets the element at index 2 to be 3
|-
|<code>del demolist[2]</code>
|removes the element at index 2
|-
|<code>len(demolist)</code>
|returns the length of <code>demolist</code>
|-
|<code>"value" in demolist</code>
|is ''True'' if <tt>"value"</tt> is an element in <code>demolist</code>
|-
|<code>"value" not in demolist</code>
|is ''True'' if <code>"value"</code> is not an element in <code>demolist</code>
|-
|<code>demolist.sort()</code>
|sorts <code>demolist</code>
|-
|<code>demolist.index("value")</code>
|returns the index of the first place that <code>"value"</code> occurs
|-
|<code>demolist.append("value")</code>
|adds an element <code>"value"</code> at the end of the list
|-
|<code>demolist.remove("value")</code>
|removes the first occurrence of value from <code>demolist</code> (same as <code>del demolist[demolist.index("value")]</code>)
|-
|<code>onetoten = range(1, 11)</code>
|-
|list[-1]
|Returns the last index
|-
|list[-2]
|Returns the second last index
|-
|things[4:7]
|Pick slice of list
|}
 
=for loop=
=for loop=
  demolist = ['life', 42, 'the universe', 6, 'and', 9, 'everything']
  fruits = ["apple", "banana", "cherry"]
  for item in demolist:
  for x in fruits:
    print item
  print(x)
=dictionary=
=range=
Add an empty dictonary called words
  for i in range(0,Loops,1):
words = {}
    print("Value")
Create a list of keys in dictionary.
  for x in words.keys():


Grabs the words in a dictionary.
=input=
Print meaning of word
Read a value from prompt into variable number.
  print words[x]
number=int(input("Please give me a number? "))
If name exist in dictionary, remove it.  
=append=
  if name in words:
Append values to grades
  del words[name]
grades.append(int(input("Please give me the grade? ")))
=format=
Use variable i input question string.
sales = float(input("Please enter your sales from day {}".format(x)))
=round, number of decimals=
  print(round(AverageGrades),1)
=debug/trace=
python -m trace --trace script.py
=virtualenvwrapper=
enter
  workon
exit
deactivate

Latest revision as of 10:51, 10 September 2024

version

Show python version 

python -V

make an http request

import requests
r =requests.get('https://halfface.se')
print(r.text)

dictionary

dictionary = {"a": 99, "hello": "world"}

import

Import functions. 

import $module

try:

Exception handling. Example will fail because x is unset. 

try:
  print(x)
except:
  print("An exception occurred")

sys.exit()

exits and no stack traceback is printed.

re

Regular expression searching 

ip = re.findall(r'[0-9]+(?:\.[0-9]+){3}', config_info)

join elements in list for other output

print(', '.join(configured_ip_addresses))

for loop

fruits = ["apple", "banana", "cherry"]
for x in fruits:
  print(x)

range

for i in range(0,Loops,1):
    print("Value")

input

Read a value from prompt into variable number. 

number=int(input("Please give me a number? "))

append

Append values to grades 

grades.append(int(input("Please give me the grade? ")))

format

Use variable i input question string. 

sales = float(input("Please enter your sales from day {}".format(x)))

round, number of decimals

print(round(AverageGrades),1)

debug/trace

python -m trace --trace script.py

virtualenvwrapper

enter 

workon

exit 

deactivate
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