Python Tips

1. Python string type

1.a Python Escape Characters

# \n : to break lines within a string
# \t : to add tab spacing between strings
# \\ : to represent the backslash character () as it is
# \' : to represent the single quote character (') as it is
# \" : to represent the double quote character (") as it is
# \r : Carriage return (line break character, moves the cursor to the beginning of the current line)
# \f : Form feed (line break character, moves the cursor to the next line)
# \a : Bell sound (when printed, emits a 'beep' sound from the PC speaker)
# \b : Backspace
# \000 : Null character

1.b F-string formatting in python

# f-string was introduced in Python 3.6, so it is invalid in Python versions lower than 3.6.

y = 3.42134234
f'{y:0.4f}' # up to 4 decimal places

'3.4213'

f'{y:10.4f}' # up to 4 decimal places and set the total number of digits to 10.

'    3.4213'

2. Dictionary type

a = {'name':'pey', 'phone':'010-9999-1234', 'birth': '1118'}
print(a.get('nokey')) # Return 'None'

None

print(a['nokey’]) # Return error

  Cell In[8], line 1
    print(a['nokey’]) # Return error
            ^
SyntaxError: unterminated string literal (detected at line 1)

a.get('nokey', 'foo') # When the key is in the dictionary, return the default value 'foo'

'foo'

3. ‘for’ and ‘continue’

marks = [90, 25, 67, 45, 80]
number = 0 
for mark in marks: 
    number = number +1 
    if mark < 60:
        continue 
    print("student #%d passed the exam. " % number)

student #1 passed the exam. 
student #3 passed the exam. 
student #5 passed the exam. 

4. list comprehension

a = [1,2,3,4]
result = []
for num in a:
    result.append(num*3)

print(result)

[3, 6, 9, 12]

result = [num * 3 for num in a]
print(result)

[3, 6, 9, 12]

result = [num * 3 for num in a if num % 2 == 0] # If you want to multiply 3 to even numbers only
print(result)

[6, 12]

5. Functions

5.1 *args

def add_many(*args): # '*' converts arguments into tuple format
    result = 0 
    for i in args: 
        result = result + i   # add all numbers from *args
    return result

result = add_many(1, 2, 3)
print(result)
result = add_many(1, 2, 3, 4, 5)
print(result)

6
15

5.b Keyword Arguments **kwargs

def print_kwargs(**kwargs): # '**' converts arguments into dictionary format
    print(kwargs) 

print_kwargs(a=1)

{'a': 1}

print_kwargs(name='foo', age=3)

{'name': 'foo', 'age': 3}

6. Print

for i in range(5):
    print(i)

0
1
2
3
4

for i in range(5):
    print(i, end=' ') # Default 'end' is '\n'

0 1 2 3 4 

7. Python Decorator

import time

def elapsed(original_func):   # Receives the original function as an argument.
    def wrapper():
        start = time.time()
        result = original_func()    # Executes the original function
        end = time.time()
        print("Function execution time: %f seconds" % (end - start))  # Prints the execution time of the original function.
        return result  # Returns the result of the original function.
    return wrapper

def myfunc():
    print("Function is being executed.")

decorated_myfunc = elapsed(myfunc)
decorated_myfunc()

Function is being executed.
Function execution time: 0.000403 seconds