python programming language
Learn from examples
I have python 2 installed as python2 .py files
I have python 3 installed as python3 .py3 files
typically, just python is now up to date python3 (my .py3 files)
1. Program to output an integer, a string,
and a floating point number, initially just one method.
exp1.py source code
# exp1.py first example simple output integer, string, double
# note # makes rest of line a comment
i = 7 # declare variable i with initial value 7
ac = 'a' # single character no type required
msg = "sample string" # declare msg with string in quotes
x = 37.95 # declare floating point x with initial value
y = 127.34e10 # declare double precision with initial value
print "exp1.py running" # simple print title
print "i=", # for decimal "," prevents end of line
print i # value after i=
print "ac=", # for character
print ac
print "msg=", # for string
print msg
print "x=", # for simple floating point
print x
print "y=", # for double with exponent
print y
exp1_py.out Output from execution:
exp1.py running
i= 7
ac= a
msg= sample string
x= 37.95
y= 1.2734e+12
exp1.py3 source code
# exp1.py3 first example simple output integer, string, double
# note # makes rest of line a comment
i = 7 # declare variable i with initial value 7
ac = 'a' # single character no type required
msg = "sample string" # declare msg with string in quotes
x = 37.95 # declare floating point x with initial value
y = 127.34e10 # declare double precision with initial value
print("exp1.py3 running") # simple print title
print("i=", i) # for decimal
print("ac=", ac) # for character
print("msg=",msg) # for string
print("x=",x) # for simple floating point
print("y=",y) # for double with exponent
print("x=%6.3f"%(x)) # using format
print("y=%g"%(y)) # using format
exp1_py3.out Output from execution:
exp1.py3 running
i= 7
ac= a
msg= sample string
x= 37.95
y= 1273400000000.0
x=37.950
y=1.2734e+12
2. commands to compile and execute the source code
at a minimum, Windows, Linux, MacOSX.
Windows:
python exp1.py
python3 exp1.py3
Linux:
python exp1.py
python3 exp1.py3
MacOSX
python exp1.py
python3 exp1.py3
To save output in a file:
python exp1.py > exp1_py.out
python3 exp1.py3 > exp1_py3.out
3. You must be able to declare variables and list and arrays
and matrix of various types.
exp3.py source code
# exp3.py example file more complete structure, list, arrays, matrix
import math
from numpy import array # for vector and matrix
def main():
print "exp3.py running"
a_list=[7, 7.25, "abc"] # any types
print "a_list=",
print a_list
print "a_list[2]=", # selecting item 2, start with 0
print a_list[2]
a_list.append("def") # append to end of list
print "append=",
print a_list
del a_list[1] # delete a selected item
print "delete=",
print a_list
print "len(a_list)=",
print len(a_list) # get the length of a list
print " "
a_tuple=2, 3, 5, 7 # can not modify all same type
b_tuple=(2, 3, 5, 7) # same data as above all same type
print "a_tuple=",
print a_tuple
print "b_tuple=",
print b_tuple
print "b_tuple[2]=", # select item 2 for printing
print b_tuple[2]
# b_tuple[2] = 9 # no modify selected item
print " "
dict={1:'a', 2:'b', 3:'c'} # dictionary key : value
print "dict=",
print dict
dict[5]='e'
print "dict 5=",
print dict
print "dict[3]=", # look up by key
print dict[3]
print " "
z=range(5) # zero based, length 5, no 5
print "range(5)=",
print z
z=range(1,5) # 1 based, length 4, no 5
print "range(1,5)=",
print z
z=range(1,7,2) # step size 2, no 7
print "range(1,7,2)=",
print z
print " "
Y = array([0.0 for i in range(4)]) # initialize to zero
print "array([0.0 for i in range(4)])="
print Y
A = array([[1.0 for j in range(4)] for i in range(3)]) # initialize to 1
print "array([1.0 for j in range(4)] for i in range(3)])="
print A
A[2,3] = 2.0
print "A[2,3] = 2.0 # then A="
print A
print " "
if __name__ == '__main__':
main()
exp3_py.out Output from execution:
exp3.py running
a_list= [7, 7.25, 'abc']
a_list[2]= abc
append= [7, 7.25, 'abc', 'def']
delete= [7, 'abc', 'def']
len(a_list)= 3
a_tuple= (2, 3, 5, 7)
b_tuple= (2, 3, 5, 7)
b_tuple[2]= 5
dict= {1: 'a', 2: 'b', 3: 'c'}
dict 5= {1: 'a', 2: 'b', 3: 'c', 5: 'e'}
dict[3]= c
range(5)= [0, 1, 2, 3, 4]
range(1,5)= [1, 2, 3, 4]
range(1,7,2)= [1, 3, 5]
array([0.0 for i in range(4)])=
[ 0. 0. 0. 0.]
array([1.0 for j in range(4)] for i in range(3)])=
[[ 1. 1. 1. 1.]
[ 1. 1. 1. 1.]
[ 1. 1. 1. 1.]]
A[2,3] = 2.0
[[ 1. 1. 1. 1.]
[ 1. 1. 1. 1.]
[ 1. 1. 1. 2.]]
exp3.py3 source code
# exp3.py3 example file more complete structure, list, arrays, matrix
import math
from numpy import array # for vector and matrix
def main():
print("exp3.py3 running")
a_list=[7, 7.25, "abc"] # any types
print("a_list=",a_list)
print("a_list[2]=",a_list[2]) # selecting item 2, start with 0
a_list.append("def") # append to end of list
print("append=",a_list)
del a_list[1] # delete a selected item
print("delete=",a_list)
print("len(a_list)=",len(a_list)) # get the length of a list
print(" ")
a_tuple=2, 3, 5, 7 # can not modify all same type
b_tuple=(2, 3, 5, 7) # same data as above all same type
print("a_tuple=",a_tuple)
print("b_tuple=",b_tuple)
print("b_tuple[2]=",b_tuple[2]) # select item 2 for printing
# b_tuple[2] = 9 # no modify selected item
print(" ")
dict={1:'a', 2:'b', 3:'c'} # dictionary key : value
print("dict=",dict)
dict[5]='e'
print("dict[5]=e",dict)
print("dict[3]=",dict[3]) # look up by key
print(" ")
z=range(5) # zero based, length 5, no 5
print("range(5)=",z)
z=range(1,5) # 1 based, length 4, no 5
print("range(1,5)=",z)
z=range(1,7,2) # step size 2, no 7
print("range(1,7,2)=",z)
print(" ")
Y = array([0.0 for i in range(4)]) # initialize to zero
print("array([0.0 for i in range(4)])=")
print(Y)
A = array([[1.0 for j in range(4)] for i in range(3)]) # initialize to 1
print("array([1.0 for j in range(4)] for i in range(3)])=")
print(A)
A[2,3] = 2.0
print("A[2,3] = 2.0")
print(A)
print(" ")
if __name__ == '__main__':
main()
exp3_py3.out Output from execution:
exp3.py3 running
a_list= [7, 7.25, 'abc']
a_list[2]= abc
append= [7, 7.25, 'abc', 'def']
delete= [7, 'abc', 'def']
len(a_list)= 3
a_tuple= (2, 3, 5, 7)
b_tuple= (2, 3, 5, 7)
b_tuple[2]= 5
dict= {1: 'a', 2: 'b', 3: 'c'}
dict[5]=e {1: 'a', 2: 'b', 3: 'c', 5: 'e'}
dict[3]= c
range(5)= range(0, 5)
range(1,5)= range(1, 5)
range(1,7,2)= range(1, 7, 2)
array([0.0 for i in range(4)])=
[ 0. 0. 0. 0.]
array([1.0 for j in range(4)] for i in range(3)])=
[[ 1. 1. 1. 1.]
[ 1. 1. 1. 1.]
[ 1. 1. 1. 1.]]
A[2,3] = 2.0
[[ 1. 1. 1. 1.]
[ 1. 1. 1. 1.]
[ 1. 1. 1. 2.]]
4. You need to be able to have loops, iteration statements
exp4.py source code
# exp4.py example file loops, iteration
def main():
print "exp4.py running"
print "for i in range(5):"
for i in range(5): # : required, indent loop, blank line terminates
print i
print "for i in range(1,6):"
for i in range(1,6): # starting value, stop at 6-1 or i<6
print i
print "for i in range(1,8,2):"
for i in range(1,8,2): # increment by 2 i=1; i<8; i=i+2
print i
print "bad for x in range(-1.5,1.5,0.5): range must be integer"
print "while x < 1.5:"
x = -1.5
print x
while x < 1.5: # while must have : blank line end of while
x = x + 0.5
print x
if __name__ == '__main__':
main()
exp4_py.out Output from execution:
exp4.py running
for i in range(5):
0
1
2
3
4
for i in range(1,6):
1
2
3
4
5
for i in range(1,8,2):
1
3
5
7
bad for x in range(-1.5,1.5,0.5): range must be integer
while x < 1.5:
-1.5
-1.0
-0.5
0.0
0.5
1.0
1.5
exp4.py3 source code
# exp4.py3 example file loops, iteration
def main():
print("exp43.py running")
print("for i in range(5):")
for i in range(5): # : required, indent loop, blank line terminates
print(i)
print("for i in range(1,6):")
for i in range(1,6): # starting value, stop at 6-1 or i<6
print(i)
print("for i in range(1,8,2):")
for i in range(1,8,2): # increment by 2 i=1; i<8; i=i+2
print(i)
print("bad for x in range(-1.5,1.5,0.5): range must be integer")
print("while x < 1.5:")
x = -1.5
print(x)
while x < 1.5: # while must have : blank line end of while
x = x + 0.5
print(x)
if __name__ == '__main__':
main()
exp4_py3.out Output from execution:
exp4.py3 running
for i in range(5):
0
1
2
3
4
for i in range(1,6):
1
2
3
4
5
for i in range(1,8,2):
1
3
5
7
bad for x in range(-1.5,1.5,0.5): range must be integer
while x < 1.5:
-1.5
-1.0
-0.5
0.0
0.5
1.0
1.5
5. You need if then else conditional statements
exp5.py source code
# exp5.py example file if, elif, else conditional statements
def main():
print "exp5.py running"
a = 3
b = 4
print "simple if ab:"
if a > b: # this will be False
print "a > b"
else: # else: in same column or same tabs as "if"
print "not a>b"
print " elif part else part if a>b:"
if a > b: # this will be False only one elif can execute
print "a > b"
elif a >= b:
print "a >= b"
elif a == b:
print "a == b"
elif a != b:
print "a != b" # True, prints
elif a <= b:
print "a <= b"
else: # not run because elif above True
print "a>b"
print "and or not in if"
if (a > b and a !=b) or a == b:
print "False"
elif not a == b:
print "not a == b"
else: # else: in same column or same tabs as "if"
print "a < b"
me = True
if me:
print "me = True"
if __name__ == '__main__':
main()
exp5_py.out Output from execution:
exp5.py running
simple if ab:
not a>b
elif part else part if a>b:
a != b
and or not in if
not a == b
me = True
exp5.py3 source code
# exp5.py3 example file if, elif, else conditional statements
def main():
print("exp5.py3 running")
a = 3
b = 4
print("simple if ab:")
if a > b: # this will be False
print("a > b")
else: # else: in same column or same tabs as "if"
print("not a>b")
print(" elif part else part if a>b:")
if a > b: # this will be False only one elif can execute
print("a > b")
elif a >= b:
print("a >= b")
elif a == b:
print("a == b")
elif a != b:
print("a != b") # True, prints
elif a <= b:
print("a <= b")
else: # not run because elif above True
print("a>b")
print("and or not in if")
if (a > b and a !=b) or a == b:
print("False")
elif not a == b:
print("not a == b")
else: # else: in same column or same tabs as "if"
print("a < b")
me = True
if me:
print("me = True")
if __name__ == '__main__':
main()
exp5_py3.out Output from execution:
exp5.py3 running
simple if ab:
not a>b
elif part else part if a>b:
a != b
and or not in if
not a == b
me = True
6. You need to be able to create functions, procedures,
subroutines.
exp6.py source code
# exp6.py example file create functions, procedures, subroutines
def jp(): # trivial just print, must have : indent, blank line
print "jp() running"
def add2(a,b): # input values and return a value (any types)
return a+b
def rtnmany(a,b): # more than one value returned
c = a+b
d = a-b
e = a*b
f = a/b
return c,d,e,f
def main():
print "exp6.py running"
jp()
c = add2(3,5)
print "c=",
print c
v1,v2,v3,v4 = rtnmany(6,3)
print v1,v2,v3,v4
if __name__ == '__main__':
main()
exp6_py.out Output from execution:
exp6.py running
jp() running
c= 8
9 3 18 2
exp6.py3 source code
# exp6.py3 example file create functions, procedures, subroutines
def jp(): # trivial just print, must have : indent, blank line
print("jp() running")
def add2(a,b): # input values and return a value (any types)
return a+b
def rtnmany(a,b): # more than one value returned
c = a+b
d = a-b
e = a*b
f = a/b
return c,d,e,f
def main():
print("exp6.py3 running")
jp()
c = add2(3,5)
print("c=",c)
v1,v2,v3,v4 = rtnmany(6,3)
print(v1,v2,v3,v4)
if __name__ == '__main__':
main()
exp6_py3.out Output from execution:
exp6.py3 running
jp() running
c= 8
9 3 18 2.0
7. You need to be able to read and write files in various formats.
exp7.py source code
# exp7.py example file read and write files of various types
def main():
line1 = "line1\n" # needs \n new line
line2 = "line2\n"
line3 = "line3\n"
print "exp7.py running"
print "write a file exp7file.txt"
file7 = open("exp7file.txt","w") # open a file for writing
file7.write(line1) # creates file, overwrites if exists
file7.write(line2)
file7.write(line3)
file7.close() # close the file
print "file written"
print "read the entire file just written"
inp = open("exp7file.txt","r") # open existing file for reading
inputs = inp.read() # reads entire file
inp.close() # close the file
print "read from exp7file.txt file"
print inputs
print "read a line at a time"
inp = open("exp7file.txt","r") # open existing file for reading
input1 = inp.readline() # reads one line
print input1
input1 = inp.readline() # reads next line
print input1
input1 = inp.readline() # reads next line
print input1
inp.close() # close the file
# read numbers from file
print "read numbers from file data.txt"
with open('data.txt') as f:
polyShape = []
for line in f:
line = line.split() # to deal with blank
if line: # lines (ie skip them)
line = [int(i) for i in line]
polyShape.append(line)
print polyShape
if __name__ == '__main__':
main()
exp7_py.out Output from execution:
exp7.py running
write a file exp7file.txt
file written
read the entire file just written
read from exp7file.txt file
line1
line2
line3
read a line at a time
line1
line2
line3
read numbers from file data.txt
[[0, 0, 3, 50], [50, 100, 3, 20]]
data.txt data file
exp7.py3 source code
# exp7.py3 example file read and write files of various types
def main():
line1 = "line1\n" # needs \n new line
line2 = "line2\n"
line3 = "line3\n"
print("exp73.py running")
print("write a file exp7file.txt")
file7 = open("exp7file.txt","w") # open a file for writing
file7.write(line1) # creates file, overwrites if exists
file7.write(line2)
file7.write(line3)
file7.close() # close the file
print("file written")
print("read the entire file just written")
inp = open("exp7file.txt","r") # open existing file for reading
inputs = inp.read() # reads entire file
inp.close() # close the file
print("read from exp7file.txt file and print")
print(inputs)
print("read a line at a time")
inp = open("exp7file.txt","r") # open existing file for reading
input1 = inp.readline() # reads one line
print(input1)
input1 = inp.readline() # reads next line
print(input1)
input1 = inp.readline() # reads next line
print(input1)
inp.close() # close the file
# read numbers from file
print("read numbers from file data.txt")
with open('data.txt') as f:
polyShape = []
for line in f:
line = line.split() # to deal with blank
if line: # lines (ie skip them)
line = [int(i) for i in line]
polyShape.append(line)
print(polyShape)
if __name__ == '__main__':
main()
exp7_py3.out Output from execution
exp73.py running
write a file exp7file.txt
file written
read the entire file just written
read from exp7file.txt file and print
line1
line2
line3
read a line at a time
line1
line2
line3
read numbers from file data.txt
[[0, 0, 3, 50], [50, 100, 3, 20]]
data.txt data file
8. You need to be able to use a number of files combined to
build a program. This may include packages, libraries,
operating system commands, header files, etc.
exp8.py source code
# exp8.py example file other functions
def main():
print "exp8.py running"
a = str(1.0/7.0) # '0.142857142857'
print a
b = repr(1.0/7.0) # '0.14285714285714285'
print b
c = len(b)
print "c=len(b) =",
print c
# Here are two ways to write a table of squares and cubes:
for x in range(1, 5):
print repr(x).rjust(2), repr(x*x).rjust(3),
print repr(x*x*x).rjust(4)
print " "
for x in range(1,5):
print '{0:2d} {1:3d} {2:4d}'.format(x, x*x, x*x*x)
# read numbers from file
with open('data.txt') as f:
polyShape = []
for line in f:
line = line.split() # to deal with blank
if line: # lines (ie skip them)
line = [int(i) for i in line]
polyShape.append(line)
print polyShape
if __name__ == '__main__':
main()
exp8_py.out Output from execution:
exp8.py running
0.14285714285714285
0.14285714285714285
c=len(b) = 19
1 1 1
2 4 8
3 9 27
4 16 64
1 1 1
2 4 8
3 9 27
4 16 64
[[0, 0, 3, 50], [50, 100, 3, 20]]
exp8.py3 source code
# exp8.py3 example file other functions
def main():
print("exp8.py3 running")
a = str(1.0/7.0) # '0.142857142857'
print(a)
b = repr(1.0/7.0) # '0.14285714285714285'
print(b)
c = len(b)
print("c=len(b) =",c)
# Here are two ways to write a table of squares and cubes:
for x in range(1, 5):
print(repr(x).rjust(2), repr(x*x).rjust(3),
repr(x*x*x).rjust(4))
print(" ")
for x in range(1,5):
print('{0:2d} {1:3d} {2:4d}'.format(x, x*x, x*x*x))
# read numbers from file
with open('data.txt') as f:
polyShape = []
for line in f:
line = line.split() # to deal with blank
if line: # lines (ie skip them)
line = [int(i) for i in line]
polyShape.append(line)
print(polyShape)
if __name__ == '__main__':
main()
exp8_py3.out Output from execution:
exp8.py3 running
0.14285714285714285
0.14285714285714285
c=len(b) = 19
1 1 1
2 4 8
3 9 27
4 16 64
1 1 1
2 4 8
3 9 27
4 16 64
[[0, 0, 3, 50], [50, 100, 3, 20]]
Python packages, such as numpy, can list the names of their functions.
The list can be very long and is one string, using dir().
print(dir(numpy.matlib)) is shown in next example:
test_numpy.py source code
test_numpy_py.out Output of execution
test_numpy.py3 source code
test_numpy_py3.out Output of execution
time_thread.py source code
time_thread_py.out Output of execution
time_thread.py3 source code
time_thread_py3.out Output of execution
Other links:
read_command_arg.py3 source code
read_command_arg_py3.out1
read_command_arg_py3.out2
read_command_arg_py3.out3
read_command_arg_py3.out4
read_keyboard.py3 source code
read_keyboard_py3.out output
Other links using tkinter for graphics:
w1tk.py source code
# w1tk.py python using Tkinter, see web for documentation
from Tkinter import *
root=Tk()
root.title('w1tk.py click to exit')
def mouseB1press(event): # left
sys.exit()
c=Canvas(root, width=200, height=100, bg='white')
c.create_line( 50, 50,150, 50,fill='black')
c.create_line(150, 50,150, 75,fill='black')
c.create_line(150, 75, 50, 75,fill='black')
c.create_line( 50, 75, 50, 50,fill='black')
c.create_text(100,30, text='click here to exit', fill='black')
c.bind('' , mouseB1press)
c.pack()
root.mainloop()
Output from execution:
w1tk.py3 source code
w1tkxy.py3 source code with x,y
Output from w1tkxy.py3 on windows:
red dashed line different on Linux
w2tk.py3 source code
w3tk.py3 source code
w4tk.py3 source code
w5tk.py3 source code
rubber_box.py3 source code
colorw.py3 source code
puzzel.py3 source code
many python 3 changes
Now, you are ready for a more complete language summary
Last updated 3/9/2022