วันที่ 4 — สตริง (Strings)

letter = 'P'                # A string could be a single character or a bunch of texts
print(letter)               # P
print(len(letter))          # 1
greeting = 'Hello, World!'  # String could be made using a single or double quote,"Hello, World!"
print(greeting)             # Hello, World!
print(len(greeting))        # 13
sentence = "I hope you are enjoying 30 days of Python Challenge"
print(sentence)

multiline_string = '''I am a teacher and enjoy teaching.
I didn't find anything as rewarding as empowering people.
That is why I created 30 days of python.'''
print(multiline_string)

# Another way of doing the same thing
multiline_string = """I am a teacher and enjoy teaching.
I didn't find anything as rewarding as empowering people.
That is why I created 30 days of python."""
print(multiline_string)

first_name = 'Asabeneh'
last_name  = 'Yetayeh'
space      = ' '
full_name  = first_name + space + last_name
print(full_name) # Asabeneh Yetayeh
# Checking the length of a string using len() built-in function
print(len(first_name))  # 8
print(len(last_name))   # 7
print(len(first_name) > len(last_name)) # True
print(len(full_name)) # 16

print('I hope everyone is enjoying the Python Challenge.\nAre you ?') # line break
print('Days\tTopics\tExercises') # adding tab space or 4 spaces
print('Day 1\t5\t5')
print('Day 2\t6\t20')
print('Day 3\t5\t23')
print('Day 4\t1\t35')
print('This is a backslash  symbol (\\)') # To write a backslash
print('In every programming language it starts with \"Hello, World!\"') # to write a double quote inside a single quote

# output
# I hope every one is enjoying the Python Challenge.
# Are you ?
# Days  Topics  Exercises
# Day 1 5       5
# Day 2 6       20
# Day 3 5       23
# Day 4 1       35
# This is a backslash  symbol (\)
# In every programming language it starts with "Hello, World!"

# Strings only
first_name = 'Asabeneh'
last_name  = 'Yetayeh'
language   = 'Python'
formated_string = 'I am %s %s. I teach %s' %(first_name, last_name, language)
print(formated_string)

# Strings  and numbers
radius = 10
pi     = 3.14
area   = pi * radius ** 2
formated_string = 'The area of circle with a radius %d is %.2f.' %(radius, area) # 2 refers the 2 significant digits after the point

python_libraries = ['Django', 'Flask', 'NumPy', 'Matplotlib','Pandas']
formated_string = 'The following are python libraries:%s' % (python_libraries)
print(formated_string) # "The following are python libraries:['Django', 'Flask', 'NumPy', 'Matplotlib','Pandas']"

first_name = 'Asabeneh'
last_name  = 'Yetayeh'
language   = 'Python'
formated_string = 'I am {} {}. I teach {}'.format(first_name, last_name, language)
print(formated_string)
a = 4
b = 3

print('{} + {} = {}'.format(a, b, a + b))
print('{} - {} = {}'.format(a, b, a - b))
print('{} * {} = {}'.format(a, b, a * b))
print('{} / {} = {:.2f}'.format(a, b, a / b)) # limits it to two digits after decimal
print('{} % {} = {}'.format(a, b, a % b))
print('{} // {} = {}'.format(a, b, a // b))
print('{} ** {} = {}'.format(a, b, a ** b))

# output
# 4 + 3 = 7
# 4 - 3 = 1
# 4 * 3 = 12
# 4 / 3 = 1.33
# 4 % 3 = 1
# 4 // 3 = 1
# 4 ** 3 = 64

# Strings  and numbers
radius = 10
pi     = 3.14
area   = pi * radius ** 2
formated_string = 'The area of a circle with a radius {} is {:.2f}.'.format(radius, area) # 2 digits after decimal
print(formated_string)

a = 4
b = 3
print(f'{a} + {b} = {a +b}')
print(f'{a} - {b} = {a - b}')
print(f'{a} * {b} = {a * b}')
print(f'{a} / {b} = {a / b:.2f}')
print(f'{a} % {b} = {a % b}')
print(f'{a} // {b} = {a // b}')
print(f'{a} ** {b} = {a ** b}')

language = 'Python'
a,b,c,d,e,f = language # unpacking sequence characters into variables
print(a) # P
print(b) # y
print(c) # t
print(d) # h
print(e) # o
print(f) # n

language     = 'Python'
first_letter = language[0]
print(first_letter) # P
second_letter = language[1]
print(second_letter) # y
last_index    = len(language) - 1
last_letter   = language[last_index]
print(last_letter) # n

language    = 'Python'
last_letter = language[-1]
print(last_letter) # n
second_last = language[-2]
print(second_last) # o

language    = 'Python'
first_three = language[0:3] # starts at zero index and up to 3 but not include 3
print(first_three) #Pyt
last_three  = language[3:6]
print(last_three)  # hon
# Another way
last_three = language[-3:]
print(last_three)  # hon
last_three = language[3:]
print(last_three)  # hon

greeting = 'Hello, World!'
print(greeting[::-1]) # !dlroW ,olleH

language = 'Python'
pto = language[0:6:2] #
print(pto) # Pto

challenge = 'thirty days of python'
print(challenge.capitalize()) # 'Thirty days of python'

challenge = 'thirty days of python'
print(challenge.count('y')) # 3
print(challenge.count('y', 7, 14)) # 1, 
print(challenge.count('th')) # 2

challenge = 'thirty days of python'
print(challenge.endswith('on'))   # True
print(challenge.endswith('tion')) # False

challenge = 'thirty\tdays\tof\tpython'
print(challenge.expandtabs())   # 'thirty  days    of      python'
print(challenge.expandtabs(10)) # 'thirty    days      of        python'

challenge = 'thirty days of python'
print(challenge.find('y'))  # 5
print(challenge.find('th')) # 0

challenge = 'thirty days of python'
print(challenge.rfind('y'))  # 16
print(challenge.rfind('th')) # 17

first_name = 'Asabeneh'
last_name  = 'Yetayeh'
age        = 250
job        = 'teacher'
country    = 'Finland'
sentence = 'I am {} {}. I am a {}. I am {} years old. I live in {}.'.format(first_name, last_name, job, age, country)
print(sentence) # I am Asabeneh Yetayeh. I am 250 years old. I am a teacher. I live in Finland.

radius = 10
pi     = 3.14
area   = pi * radius ** 2
result = 'The area of a circle with radius {} is {}'.format(str(radius), str(area))
print(result) # The area of a circle with radius 10 is 314.0

challenge  = 'thirty days of python'
sub_string = 'da'
print(challenge.index(sub_string))  # 7
print(challenge.index(sub_string, 9)) # error

challenge  = 'thirty days of python'
sub_string = 'da'
print(challenge.rindex(sub_string))  # 7
print(challenge.rindex(sub_string, 9)) # error
print(challenge.rindex('on', 8)) # 19

challenge = 'ThirtyDaysPython'
print(challenge.isalnum()) # True

challenge = '30DaysPython'
print(challenge.isalnum()) # True

challenge = 'thirty days of python'
print(challenge.isalnum()) # False, space is not an alphanumeric character

challenge = 'thirty days of python 2019'
print(challenge.isalnum()) # False

challenge = 'thirty days of python'
print(challenge.isalpha()) # False, space is once again excluded
challenge = 'ThirtyDaysPython'
print(challenge.isalpha()) # True
num = '123'
print(num.isalpha())       # False

challenge = 'thirty days of python'
print(challenge.isdecimal())  # False
challenge = '123'
print(challenge.isdecimal())  # True
challenge = '\u00B2'
print(challenge.isdigit())   # True 
challenge = '12 3'
print(challenge.isdecimal())  # False, space not allowed

challenge = 'Thirty'
print(challenge.isdigit()) # False
challenge = '30'
print(challenge.isdigit())   # True
challenge = '\u00B2'
print(challenge.isdigit())   # True

num = '10'
print(num.isnumeric()) # True
num = '\u00BD' # ½
print(num.isnumeric()) # True
num = '10.5'
print(num.isnumeric()) # False

challenge = '30DaysOfPython'
print(challenge.isidentifier()) # False, because it starts with a number
challenge = 'thirty_days_of_python'
print(challenge.isidentifier()) # True

challenge = 'thirty days of python'
print(challenge.islower()) # True
challenge = 'Thirty days of python'
print(challenge.islower()) # False

challenge = 'thirty days of python'
print(challenge.isupper()) #  False
challenge = 'THIRTY DAYS OF PYTHON'
print(challenge.isupper()) # True

web_tech = ['HTML', 'CSS', 'JavaScript', 'React']
result = ' '.join(web_tech)
print(result) # 'HTML CSS JavaScript React'

web_tech = ['HTML', 'CSS', 'JavaScript', 'React']
result = '# '.join(web_tech)
print(result) # 'HTML# CSS# JavaScript# React'

challenge = 'thirty days of pythoonnn'
print(challenge.strip('noth')) # 'irty days of py'

challenge = 'thirty days of python'
print(challenge.replace('python', 'coding')) # 'thirty days of coding'

challenge = 'thirty days of python'
print(challenge.split()) # ['thirty', 'days', 'of', 'python']
challenge = 'thirty, days, of, python'
print(challenge.split(', ')) # ['thirty', 'days', 'of', 'python']

challenge = 'thirty days of python'
print(challenge.title()) # Thirty Days Of Python

challenge = 'thirty days of python'
print(challenge.swapcase())   # THIRTY DAYS OF PYTHON
challenge = 'Thirty Days Of Python'
print(challenge.swapcase())  # tHIRTY dAYS oF pYTHON

challenge = 'thirty days of python'
print(challenge.startswith('thirty')) # True

challenge = '30 days of python'
print(challenge.startswith('thirty')) # False