# search a dictionary for key or value
 
def find_key(dic, val):
    """return the key of dictionary dic given the value"""
    return [k for k, v in symbol_dic.iteritems() if v == val][0]
 
def find_value(dic, key):
    """return the value of dictionary dic given the key"""
    return dic[key]
 
# test it out
if __name__ == '__main__':
    # dictionary of chemical symbols
    symbol_dic = {
    'C': 'carbon',
    'H': 'hydrogen',
    'N': 'nitrogen',
    'Li': 'lithium',
    'Be': 'beryllium',
    'B': 'boron'
    }
 
    print find_key(symbol_dic, 'boron')  # B
    print find_value(symbol_dic, 'B')    # boron

def clear_screen():
    """
    clear the screen in the command shell
    works on windows (nt, xp, Vista) or linux
    """
    import os
    os.system(['clear','cls'][os.name == 'nt'])
 
# test module out
if __name__ == '__main__':
    import time
    print "some text on the screen for a few seconds"
    # wait 2.5 seconds
    time.sleep(2.5)
    # now clear the screen
    clear_screen()
    # wait
    time.sleep(1.5)
    print "test completed"
    raw_input("press enter to go on ")

# count the character frequency in a text:
# create a list of unique (frequency, character) tuples
# then sort and display highest frequency characters first
 
text = 'mississippi mudslide'
 
# create a list of characters from the text
c_list = list(text)
 
# make a list of (frequency, char) tuples, use set() to avoid duplicates
fc_list = [(c_list.count(c), c) for c in set(c_list) if c.isalpha()]
 
for item in sorted(fc_list, reverse=True):
    print "%s --> %s" % (item[1], item[0])
 
"""
my output -->
s --> 5
i --> 5
p --> 2
m --> 2
d --> 2
u --> 1
l --> 1
e --> 1
"""

# count the character frequency in a text
# a slightly faster option using a dictionary instead of a set ...
from operator import itemgetter
 
text = 'mississippi mudslide'
d = {}
for c in text:
    if c.isalpha():
        d[c] = d.get(c, 0) + 1
 
for k, v in sorted(d.items(), key=itemgetter(1), reverse=True):
    print "%s --> %s" % (k, v)
 
"""
my output -->
i --> 5
s --> 5
d --> 2
m --> 2
p --> 2
e --> 1
l --> 1
u --> 1
"""

# subtract/remove elements of one list from another
 
city = ['Lisbon', 'Paris', 'Reno', 'London', 'Oslo', 'Ypsilanti']
 
visited = ['Reno', 'Ypsilanti']
 
not_visited = [c for c in city if c not in visited]
# order of remaining elements has not changed
print not_visited
 
# simpler ...
not_visited = list(set(city) - set(visited))
# order of remaining elements has changed
print not_visited
 
"""
my result --->
['Lisbon', 'Paris', 'London', 'Oslo']
['Paris', 'Oslo', 'London', 'Lisbon']
"""

    txt = txt[0] + txt[2:]

food = 'bread'
vars()[food] = 123
print bread  # --> 123

# a more secure way to enter a date
 
import datetime as dt
 
def enter_date():
    """
    asks to enter year, month and day and returns
    date info as <type 'datetime.datetime'>
    """
    def extract_date(s):
        try:
            # month given as a decimal number
            date = dt.datetime.strptime(s, "%d %m %Y")
        except:
            try:
                # month given as a 3 letter abreviation
                date = dt.datetime.strptime(s, "%d %b %Y")
            except:
                return None
        return date
 
    while True:
        year = raw_input("Enter year (eg. 1979): ")
        # you can enter number of month, full name or 3 letter abbreviation
        month = raw_input("Enter month (eg. 9 or sep): ")
        day = raw_input("Enter the day of the month: ")
        date = extract_date(day + " " + month[:3].title() + " " + year)
        if date == None:
            print "Illegal info!"
            continue
        else:
            return date
 
 
date = enter_date()
 
# testing ...
#print date, type(date)           # 2001-09-11 00:00:00 <type 'datetime.datetime'>
#print date.strftime("%m/%d/%Y")  # 09/11/2001
#print date.strftime("%d%b%Y")    # 11Sep2001
 
# do something with it ...
today = dt.datetime.today()
age = today - date
# assumes week starts with Monday
weekdays = ['Monday', 'Tuesday', 'Wednesday', 'Thursday', 'Friday', 'Saturday', 'Sunday']
week_day = weekdays[dt.date.weekday(date)]
print "Today is %s" % today.strftime("%d%b%Y")
print "%s was %d days ago on a %s" % (date.strftime("%d%b%Y"), age.days, week_day)
 
"""
my output -->
Enter year (eg. 1979): 2001
Enter month (eg. 9 or sep): september
Enter the day of the month: 11
Today is 03Mar2008
11Sep2001 was 2365 days ago on a Tuesday
"""

# print a table (16 columns) of ASCII characters from 1 to 127
 
# Bumsfeld, thanks for the dictionary
controls_dic = {
1: 'SOH', 2: 'STX', 3: 'ETX', 4: 'EOT', 5: 'ENQ', 6: 'ACK', 7: 'BEL',
8: 'BS', 9: 'HT', 10: 'LF', 11: 'VT', 12: 'FF', 13: 'CR', 14: 'SO',
15: 'SI', 16: 'DLE', 17: 'DC1', 18: 'DC2', 19: 'DC3', 20: 'DC4', 21: 'NAK',
22: 'SYN', 23: 'ETB', 24: 'CAN', 25: 'EM', 26: 'SUB', 27: 'ESC', 28: 'FS',
29: 'GS', 30: 'RS', 31: 'US'}
 
n = 1
for k in range(1, 128):
    if k < 32:
        s = controls_dic[k]
    else:
        s = chr(k)
    if n % 16 > 0:
        print "%4s" % s,
    else:
        print "%4s" % s
    n += 1

# KeyLogger.py
# show a character key when pressed without using Enter key
# hide the Tkinter GUI window, only console shows
 
import Tkinter as tk
 
def key(event):
    if event.keysym == 'Escape':
        root.destroy()
    print event.char
 
root = tk.Tk()
print "Press a key (Escape key to exit):"
root.bind_all('<Key>', key)
# don't show the tk window
root.withdraw()
root.mainloop()