001-5. Creating function
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# Day_01_04_function.py
# Core concept of function : passing data and taking data
# parameter : data
# return value : data
# Type1:
# Funtion without parameter and return value (this type of function is rarely used)
def f_1():
print('f_1')
# Call
f_1()
# Type2:
# Funtion with parameter, without return value
def f_2(a, b):
print('f_2', a, b)
# Call
f_2(23, 'abc')
# Type3:
# Without parameter, with return value
def f_3():
# When we don't write contents in function, we get error
# In this case, we temporalily use "pass" keyword
# pass
print('f_3')
return 17
# a = return 17
a = f_3()
print(a)
print(f_3())
# Type4:
# With parameter, with return value
# Quiz: Make function which swap each digit from 2 digits positive number
def f_4(n):
return n%10*10 + n//10
print(f_4(37))
# output:73
print(f_4(82))
# output:28
# Quiz
# Make function which print largest number from 4 numbers
# But, don't directly print the largest number
# in function by using print() inside of function
# You can use "return" multiple times
# But it's recommended to use one time
def max_from_4(a, b, c, d):
# return max_from_2(max2(a, b), max_from_2(c, d))
return max_from_2(max_from_2(max_from_2(a, b), c), d)
# Sub quiz(easy version)
# Make function which print largest number from 2 numbers
def max_from_2(a, b)
if a >= b:
return a
else:
return b
# Since "return" means end of function,
# I can write as following
def max_from_2(a, b)
if a >= b:
return a
return b
# Let's try to use "return" one time
# If b is greater than a, I print b
# If a is greater than b, I overwrite a onto b, and then, print overwritten b
def max_from_2(a, b)
if a >= b:
b = a
return b
print(max_from_2(3, 7))
print(max_from_2(7, 3))
print(max_from_4(1, 2, 3, 4))
print(max_from_4(4, 1, 2, 3))
print(max_from_4(3, 4, 1, 2))
print(max_from_4(4, 1, 2, 3))
# One of the greatest reasons to write function is reusability
# Since I already verified max_from_2() works well,
# it's fair to say max_from_4() will work well
# Function contributes to stability
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