Download τυπολογιο python

ΤΥΠΟΛΟΓΙΟ PYTHON
Compact summary of python
This is not intended to be the complete language.
name your file
execute your file
on MS Windows only
when using Tk, wx, Qt
xxx.py
python xxx.py
pythonw xxx.py
execute your file and save output in a file
python xxx.py > xxx.out
# rest of line is a comment, # sign makes the rest of a line a
comment
"""
"""
starts a long comment, can be many lines
# ends the long comment
Indentation must remain the same on a sequence of statements.
(statements starting next indentation, end with a colon : )
Indent after each compound statement such as if, while, for, def ...
print "hello from python" # quotes make strings, writes to display
print 'hello from python' # apostrophes make strings, no character type
print "hello",
print "from python" # because of previous comma, writes same one line
# see files hello.py and hello.out
print x # prints the value of x, any type
print "x=",
print x # prints one line, e.g. x= 7.25e-27
Strings may use either " or ' (same on both ends)
Open a file for reading or writing, f is any variable name
f=open("myfile.dat", "r")
f=open("myfile.dat", "w")
f.close()
a=f.read()
a=readline()
string
a
f.seek(5)
#
#
#
#
#
open for reading
open for writing
close the file
read entire file into string a
read one line, including \ n, into
# seek five
# see files testio.py and testio.out
Reserved words:
and
elif
if
as
assert
else except
import
in
break
class
exec
finally
is
lambda
not
[1]
continue
def
del
for
from global
or
pass
print
raise
return
try
while
with
yield
Operators:
y=7
z=5.3
x=y+z
x=-y
x+=1
# the usual assignment statements with normal precedence
# in place of x++;
the list of operators is: + - * ** / // % arithmetic
<< >> & | ^ ~ shift logical
< > <= >= != and or comparison
Delimiters include:
( ) [ ] { } @ grouping
, : . ` ; separating
= += -= *= /= //= %= operate store
&= |= ^= >>= <<= **= operate store
Special characters: ' " # \
Not used: $ ?
Numbers:
1 123456789012345678 1.3 7.5e-200 0xFF 5.9+7.2j
Boolean:
Tuples:
True False constants
x=2, 3, 5, 7, 11
y=(2, 3, 5, 7, 11)
Lists:
x=[2, 3, 5, 7, 11]
An array of 10 elements, initialized to zeros:
z=[0 for i in range(10)]
z[0]=z[9] # lowest and highest subscripts
A 2D array of 3 by 4 elements, initialized to zeros:
a=[[0 for j in range(4)] for i in range(3)]
a[0][0]=a[2][3] # lowest and highest subscripts a[i][j]
import math # see files testmath.py and testmath.out
a=math.sin(b)
print "b=%f, sin(b)=%f" % (b, a) # formatted output %d, %10.5f, %g
...
import decimal
# big decimal
a=decimal.Decimal("39.25e-200")
import random
a=random.randint(1,10)
import NumPy
import Numarray
import Numeric
# latest numerics package
# older numerics package Multiarray ?
# very old numerics package
[2]
Three equivalent ways to call QString:
from PyQt4.QtCore import * # all directly visible
x=QString()
import PyQt4.QtCore as P # any short name
x=P.QString()
import PyQt4
x=PyQt4.QtCore.QString() # fully named
You can have your own program in many files.
e.g. file spiral_trough.py has a function spiral def spiral(x,y)
in test_spiral.py from spiral_trough import spiral
z=spiral(x1,y1)
if a<b:
statements
elif c>d:
statements
elif e==f:
statements
else:
statements
# control statements zero or null is True
# anything else is False
# <= for less than or equal
# >= for greater than or equal
# != for not equal
# unindent to terminate
for i in range(n): # i=0, 1, 2, ... , n-1
for i in range(3,6): # i=3, 4, 5 not 6
for i in range(5,0,-1): # i=5, 4, 3, 2, 1 not 0
while boolean_expression: # || is "or" && is "and" True, False
"break" exits loop or "if" statement.
"continue" goes to next iteration in a loop.
Function definition and call:
def aFunction(x, y, z): # inputs of any type
# do something, compute a and b
return a,b
# somewhere later
m, n = aFunction(p, q, r) # none, one, or multiple value return
one or several functions defined in a file
# funct_to_import.py has two functions defined, funct and rabc
def funct(n):
return n
[3]
a,b,c=0,0,0
def rabc():
a=1
b="rabc string"
c=[3, 4, 5, 6]
return a,b,c
In another file, call funct and rabc
# test_import_funct.py import funct_to_import and run funct and rabc
import funct_to_import
print funct_to_import.funct(3)
print
x,y,z
print
print
print
print
funct_to_import.rabc()
= funct_to_import.rabc()
x
y
"z[1]=",
z[1]
[4]