python
learning links ↓
echo floating point with 4 digits, “argument specifier” ↓
f=3.3465922378323784
print "%.4f" % f
This should also round corectly, giving 3.3466
functions ↓
# function
def sum_two_numbers(a, b):
return a + b
# call
x = sum_two_numbers(1,2)
print x
a placeholder pass
def somefunc():
pass #this is a null statement/placeholder
Can I have functions at the bottom of the script? ↓
As sort of the gosub old basic approach
def main():
# my code
def other()
....
def another()
....
def andmore()
....
main()
People say yes.
objects ↓
# Objects are an encapsulation of variables and functions into a single entity. Objects get their variables and functions from classes. Classes are essentially a template to create your objects.
class MyClass:
variable = "blah"
def function(self):
print "This is a message inside the class."
# define object
myobjectx = MyClass() # assign the above class(template) to an object
print myobjectx.variable # the variable inside of the newly created object "myobjectx"
# another object of the same class
myobjecty = MyClass()
myobjecty.variable = "yackity" # change variable
print myobjecty.variable
dictionaries ↓
phonebook = {
"John" : 938477566,
"Jack" : 938377264,
"Jill" : 947662781
}
# write your code here
phonebook["Jake"] = 938273443
del phonebook["Jill"]
# testing code
if "Jake" in phonebook:
print "Jake is listed in the phonebook."
if "Jill" not in phonebook:
print "Jill is not listed in the phonebook."
modules ↓
http://www.learnpython.org/en/Modules_and_Packages
import urllib
# which functions are implemented in each module
dir(urllib)
# When we find the function in the module we want to use, we can read about it more using the help function, inside the Python interpreter
help(urllib.urlopen)
lost ↓
In this exercise, you will need to print an alphabetically sorted list of all functions in the re module, which contain the word find
import re
# Your code goes here
find_members = []
for member in dir(re):
if "find" in member:
find_members.append(member)
print sorted(find_members)
find_members is a list type of structure (something similar to array) and sorted is a sorting thing (function).
So if i say
somelist = [9,8,7]
print sorted(somelist)
# [7, 8, 9] < should happen
List Comprehensions ↓
Using a list comprehension, create a new list called “newlist” out of the list “numbers”, which contains only the positive numbers from the list, as integers.
After quite some trouble I got this
numbers = [34.6, -203.4, 44.9, 68.3, -12.2, 44.6, 12.7]
newlist = []
for stuff in numbers:
#print stuff
stuff = int(stuff)
if stuff > 0: # this should probably be if 'stuff >= 0:'
newlist.append(stuff)
print newlist
which does work, but the official solution is this 3 liner
numbers = [34.6, -203.4, 44.9, 68.3, -12.2, 44.6, 12.7]
newlist = [int(x) for x in numbers if x > 0] # < what is this? Yeah that is an actual 'List Comprehension'
print(newlist)
About printf style formatting ↓
# example
print "Result: %d" % result
https://en.wikipedia.org/wiki/Printf_format_string
The % results part seems to be called ‘string interpolation’.
More ways to print stuff ↓
v = 10
print('speed is', v, 'm/s')
print('speed is ' + str(v) + ' m/s')
print(f'speed is {v} m/s')
should all produce the same result.
user input ↓
var = float(input("enter the number: "))
x = var ** 2
print("result", x)
Input seems to be string, so lets convert that to float prior to math stuff.
if else while random truth ↓
from random import randint
i = 0
while i < 5:
var = randint(0, 1)
if var:
print("true")
else:
print("false")
i = i + 1
