# pass by reference
def f2(m, im):
    print '----------------Inside function-------------'
    print id(m), m; # 13977378998840, [0, 1, 2, 3, 4, 5, 6, 7, 8, 9,]
    print id(im), im; # 38097024, 10
    m.append(100);
    im = 100;
    print id(m), m # 13977378998840, [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 100]
    print id(im), im # 38098848, 100
    print '---------------Leave function--------------'

a = 10; # 38097024 10
b = range(10) # 13977378998840, [0, 1, 2, 3, 4, 5, 6, 7, 8, 9,]
print id(a), a
print id(b), b
f2(b, a);
print id(a), a # 38097024, 10
print id(b), b # 13977378998840, [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 100]
			

• All parameters (arguments) in the Python language are passed by reference
• Mutable parameters, can be modified by function
• Immutable parameters, cannot be modified by function

# default arguments
def f1(p1, p2 = 10):
    print p1, p2

f1(1)
			

# keyword arguments
def f3(p1 = 1, p2 = 2):
    print p1, p2

f3(p2 = 10)
			

# variabel-length arguments
def f4(*vartuple):
    print len(vartuple);
    print vartuple; # vartuple is a tuple
    for i in vartuple:
        print i

f4(1, 2, 3, 'end')
			

#!/usr/bin/python

# pass by reference
def f(a, b):
    print a, b;

l = [10, 20]; # singularize list or tuple
f(*l); # 10 20
			

#!/usr/bin/python

def f(**args):
    print args;
    for k in args.keys():
        print k, args[k];

f(inFile = 'input', outFile = 'output');
			

#!/usr/bin/python

def f(**args):
    print args;
    for k in args.keys():
        print k, args[k];

d = {'inFile':'input', 'outFile':'output'}; # singularize dict
f(**d);
			

#!/usr/bin/python

#lambda
sum = lambda arg1, arg2: arg1+arg2;

print sum(10, 20); #30

#map
def t(arg):
    return arg*10;

l = [1, 2, 3, 4];
print map(t, l); #[10, 20, 30, 40], use function
print map(lambda x: x*10, l); #[10, 20, 30, 40], using lambda

#filter
print filter(lambda x: x%2 == 0, l); #[2, 4]

#reduce
print reduce(lambda x, y: x+y, l); #10
			

#!/usr/bin/python

def getNums():
    return 1, 2

a, b = getNums()
print a, b # 1, 2

_, b = getNums() # use _ to hold a place
print b # 2

t = getNums()
print t # (1, 2), t is a tuple
			

#!/usr/bin/python

def getNum_1():
    return 1 # return an integer

def getNum_2():
    return # return nothing

def getNum_3():
    return None # return None

def getNum_4():
    pass # no return will return None

def main():
    if getNum_1() is None:
        print getNum_1() # not print
    if getNum_2() is None:
        print getNum_2() # None
    if getNum_3() is None:
        print getNum_3() # None
    if getNum_4() is None:
        print getNum_4() # None

if __name__ == '__main__':
    main()
			

#!/usr/bin/python

def factorial(n):
    '''factorial
    Args:
        n (int), integer number
    Return:
        int, factorial number
    '''
    if n == 0:
        return 1;
    else:
        return n*factorial(n-1);

def main():
    print factorial(10);

if __name__ == '__main__':
    main()
			

• Python’s null equivalent: None
• Tutorialspoint.com
• Recursive at Python Course
• Lambda at Python Course
• Parameter Passing at Python Course