# important built-in types: None, bool (True/False), int, long, float, str, unicode, list, dict, tuple (and some others)
n = 30.5
print str(n) # 30.5
print str(int(n)) # 30
print str(bool(n)) # True
h = 0xFF
print str(h) # 255
print chr(65) # A
print ord("A") # 65# Compare: ==, <, >, <=, >=, !=
# Bitwise: & (AND), | (OR), ^ (XOR), ~ (COMPLEMENT), << (SHIFT LEFT), >> (SHIFT RIGHT)
# Logical: and, or, not
# Escape Sequence: \\ (\), \r (CR), \n (LF), \' ('), \" ("), \t (TAB), \x41 (A), \u0000 (16bit Unicode), \U00000000 (32bit Unicode)# if, elif, else
b = True
if b == True: # short form => "if b:"
print "Yes, it's true."
else:
print "Did you change the value of b?"
# Yes, it's true.
# while
i = 2
while i > 0:
print str(i) + " > 0"
i -= 1 # i = i - 1
# 2 > 0 and 1 > 0
# for, in, range()
for i in range(2, 10, 2): # range(start = 2, stop = 10, step = 2)
print str(i)
# 2, 4, 6 and 8
# break, continue, pass
for i in range(0, 10): # range(start = 0, stop = 10, step = 1)
if i == 1:
pass # do nothing
elif i == 2:
continue # don't print 2
elif i == 5:
break # loop interruption
print str(i)
# 0, 1, 3 and 4# string[], len()
first_string = "Hello world!"
print first_string # Hello world!
print str(len(first_string)) # 12 (amount of characters => 0-11)
print first_string[:5] # Hello (characters 0-4)
print first_string[6:11] # world (characters 6-10)
print first_string[11:] # ! (character 11)
| H |
e |
l |
l |
o |
|
w |
o |
r |
l |
d |
! |
DIRECTION |
| 0 |
1 |
2 |
3 |
4 |
5 |
6 |
7 |
8 |
9 |
10 |
11 |
from left |
| -12 |
-11 |
-10 |
-9 |
-8 |
-7 |
-6 |
-5 |
-4 |
-3 |
-2 |
-1 |
from right |
# string.index(), string.count()
first_string = "Hello world!"
if "w" in first_string:
a = first_string.index("w")
print "index of 'w' in first_string"
print "a = " + str(a)
if "l" in first_string:
b = first_string.count("l")
print "amount of character 'l' = " + str(b)
# index of 'w' in first_string
# a = 6
# amount of character 'l' = 3# list, type()
l = ["This", "is", "my", "list", 1, 2, True, 30.5]
for item in l:
print str(item) + " [" + type(item).__name__ + "]"
print l[0:-4]
# This [str], is [str], my [str], list [str], 1 [int], 2 [int], True [bool] and 30.5 [float]
# ['This', 'is', 'my', 'list']
# list.remove(), .insert(), .append(), .extend(), .sort(), .reverse(), del
la = ["This", "is"]
lb = ["my", "list"]
la.extend(lb) # la = ["This", "is", "my", "list"] ### la = la + lb ###
print la
la.remove("list") # la = ["This", "is", "my"] ### del la[3] ###
print la
la.insert(3, "new") # la = ["This", "is", "my", "new"]
print la
la.append("list") # la = ["This", "is", "my", "new", "list"]
print la
la.sort() # la = ["This", "is", "list", "my", "new"]
print la
la.reverse() # la = ["new", "my", "list", "is", "This"]
print la# immutable tuple
t = ("This", "is", "a", "tuple")
del t[0] # TypeError: 'tuple' object doesn't support item deletion# dict
d = { "car" : 100, # key : value
"ship" : 70,
"plane" : 50}
print "Length of d = " + str(len(d)) # Length of d = 3
for key in d.keys():
print key # car, ship, plane
for value in d.values():
print value # 100, 70, 50
for item in d.items():
if item[1] == 70: # item = tuple = ('key', value)
print "Found " + item[0] # Found ship
value = d.get("ship") # value = 70 or None if key is missing# string.find() => find all "is" strings in s
s = "This is my test string which is much longer than this other string."
i = 0 # start position
l = [] # empty list
while i != -1:
i = s.find("is", i) # i = position or -1
if i != -1:
l.append(i)
i += 1
print l # [2, 5, 29, 51]# Regular Expressions
#
# raw_string = r"\" vs. plain_string = "\\"
# . (any char), [^a] (not a), [A-Z] (A-Z), [A-Za-z] (A-Z and a-z), [0-9] == \d (only digits)
# \s (whitespace chars), [A-Za-z0-9_] == \w
# ? (left char once or never), + (left char once or several times), * (left char not, once or several times)
# {2} (left char have to exist twice), {1,} (left char once or several times), {1,2} (left char have to exist once or twice)
#
import re
s = "This \r\nis \ta -special- string!"
l = re.split(r"[^\w]+", s) # or re.split(r"[^A-Za-z]+", s)
print l # ['This', 'is', 'a', 'special', 'string', '']# read/write textfile
# see also .readline(), .readlines(), .writelines()
filename = "data.txt"
file = open(filename, 'a') # append/create file
file.write("A new line in data.\n")
file.close()
file = open(filename, 'r') # read file
print file.read() # A new line in data.\n (every time you start the script a new line is added)
file.close()# read/write binaryfile
# see also .seek(), .tell()
filename = "data.dat"
file = open(filename, 'wb') # write/create binary file
l = [0,1,2,128,255]
b = bytearray(l)
file.write(b)
file.close()
file = open(filename, 'rb') # read binary file
s = file.read()
for item in s:
print int(item.encode('hex'), 16),
print '= 0x' + item.encode('hex') # 0 = 0x00 ... 255 = 0xff
file.close()# read/write csvfile
import csv
filename = "data.csv"
file = open(filename, 'wb') # write/create binary file
la = ['column1', 'column2', 'column3', 'column4']
lb = ['text with spaces', '1/1/2016', 4567.12, '12:00:00']
csvwriter = csv.writer(file, delimiter=';') # delimiter=',' is default
csvwriter.writerow(la)
csvwriter.writerow(lb)
file.close()
file = open(filename, 'rb') # read binary file
csvreader = csv.reader(file, delimiter=';') # delimiter=',' is default
for l in csvreader:
print l # ['column1', 'column2', 'column3', 'column4']
# ['text with spaces', '1/1/2016', '4567.12', '12:00:00']
file.close()# os.getcwd(), .path.expanduser('~'), ...
# see also .uname() and .environ for information about your os
import os
print os.getcwd() # current working directory
print os.path.expanduser('~') # user's HOME directory
print os.listdir('/') # show root directory (r'C:\' should work for Windows)
print os.path.exists(path) # True/False if file/directory exists or not (see also os.access())
print os.path.split(path) # tuple with directory-path and filename
print os.path.getsize(path) # file size in bytes# sys.version , .path, .exit()
import sys
print sys.version # Python version
print sys.path # show PYTHONPATH
sys.path.append(path) # add an additional path
sys.exit() # exit the python script (doesn't make sense at the end)
# SQLite 3
import sqlite3
sqlcon = sqlite3.connect("test.db") # sqlite.connect(":memory:") won't be stored
sqlcur = sqlcon.cursor()
sqlcur.execute("CREATE TABLE table1 (id INTEGER PRIMARY KEY, name TEXT, birthday TEXT)")
sqlcur.execute("INSERT INTO table1 (id, name, birthday) VALUES (NULL, 'myname', '2016-01-01')")
sqlcon.commit()
sqlcon.close()
sqlcon = sqlite3.connect("test.db")
sqlcur = sqlcon.cursor()
sqlcur.execute("SELECT * FROM table1")
sqldata = sqlcur.fetchone() # .fetchone() => get the first record or use .fetchall()
print sqldata
sqlcon.close()
# data types: NULL, INTEGER, REAL, TEXT and BLOB
# Delete all records in table1:
# sqlcur.execute("DELETE FROM table1")
# sqlcon.commit()
# Delete a particular record in table1:
# sqlcur.execute("DELETE FROM table1 WHERE id=0")
# sqlcon.commit()
# Delete whole table1:
# sqlcur.execute("DROP TABLE IF EXISTS table1")
# sqlcon.commit()
# Change data in a particular record in table1:
# sqlcur.execute("UPDATE table1 SET name=? WHERE id=?", (name, id))
# sqlcon.commit()
# Adding a column to a table
# sqlcur.execute("ALTER TABLE table1 ADD COLUMN 'hobby' TEXT")
# sqlcon.commit()
# Working with Variables:
# sqlcur.execute("INSERT INTO table1 VALUES (?, ?, ?)", (var1, var2, var3))
# sqlcur.execute("SELECT name, birthday FROM table1 WHERE id = (?)", (id,))
# sqlcon.commit()
# Find all tables in current database:
# sqlcur.execute("SELECT name FROM sqlite_master WHERE type='table')
# sqldata = sqlcur.fetchall()
# SELECT COUNT(*) FROM table1 # how many records are in table1?
# SELECT * FROM table1 JOIN table2 ON table1.id = table2.t1id WHERE name='myname' ORDER BY birthday;
# ORDER BY DESC birthday; # (default:ASC) / DESC (larger values first)
# SELECT name AS nickname, birthday AS bd FROM table1; # AS define an ALIAS
# SELECT t1.name, t1.birthday FROM table1 as t1; # ALIAS for table1
# SELECT t1.name, COUNT(*) AS samename FROM table1 as t1 GROUP BY t1.name; # how many users have the same name?
# search for a picture "SQL JOINS" with your favorite search engineif __name__ == '__main__':
#this code will be ignored if you import the script as moduleimport module #module.class() or module.methode()
import package.module #package.module.class() or package.module.methode()
from module import * #class() or methode()
from module import methode1, methode2 #methode1() or methode2()