Python) Datatypes - Str

Text Type:	str
Numeric Types:	int, float, complex
Sequence Types:	list, tuple, range
Mapping Type:	dict
Set Types:	set, frozenset
Boolean Type:	bool
Binary Types:	bytes, bytearray, memoryview
None Type:	NoneType

String 

s1 = 'Hello World'
print(type(s1))                 # <class 'str'>
print(s1)

s2 = "Python is fun"
print(type(s2))                 # <class 'str'>
print(s2)

s3 = '''Life is too short, you need python.'''
print(type(s3))                 # <class 'str'>
print(s3)

s4 = """Life is too short, you need python."""
print(type(s4))                 # <class 'str'>
print(s4)

Unlike other languages, in Python, you can add and multiply the strings. 

head = 'Python'
tail = ' is fun'
str = head + tail
print(str)                     
print(head + tail)             

s = 'python'
print(s * 2)                  
print(s * 3)                   

print('='*50)                 
print('My Program')
print('='*50)                  

print('*'*1)
print('*'*2)
print('*'*3)
print('*'*4)
print('*'*5)

print('*'*5)
print('*'*4)
print('*'*3)
print('*'*2)
print('*'*1)

Indexing

Indexing is used when you need to extract parts of the data. 

The first letter is index'0', and the last letter is index'-1'. 

s = 'Life is too short, you need python'
print(s)

print(s[0])                 # L
print(s[3])                 # e
print(s[-1])                # n
print(s[-2])                # o

str = 'korea'
print(str[0])               # k
print(str[-2])              # e

Slicing

Example1

# format :  variable[ start : stop ]

s = 'Life is too short, you need python'

print(s[0:2])         # 0 - 1 : Li
print(s[0:5])         # 0 - 4 : Life
print(s[5:7])         # 5 - 6 : is
print(s[12:17])       # 12 - 16 : short

print(s[ : 7])        # 0 -6 : Life is

print(s[5 : ])        # 5 - last : is too short, you need python

print(s[ : ])         # first - last


str = '20201024Rainy'
date = str[:8]              # 20201024
weather = str[8:]           # Rainy
print(date,':', weather)


year = str[:4]              # 2020
month = str[4:6]            # 10
day = str[6:8]              # 24
print(year, 'Year', month, 'Month', day, 'Day')

 

Example2

str = 'korea'

print(str[0])           # [0] : k
print(str[-2])          # The second last : e

print(str[1:3])         # 1 - 2 : or
print(str[0:5:2])       # 0 - 4 (+2) : kra
print(str[:-1])         # first - -2 : kore
print(str[::-1])        # reverse : aerok

Example3 

To change strings with slicing, you need to slice first and combine the letters.

s = 'pithon'
print(s[1])                       # i

# i -> y 
# s[1] = 'y'                      # TypeError: 'str' object does not support item assignment

s = s[:1] + 'y' + s[2:]           # python
print(s)

 

Functions

upper() / lower()

txt = 'A lot of things happen everyday.'

result1 = txt.upper()
result2 = txt.lower()

print('result1:', result1)  #result1: A LOT OF THINGS HAPPEN EVERYDAY.
print('result2:', result2)  #result2: a lot of things happen everyday.

format()

%s	String
%c	Character
%d	Integer
%f	float
%%	%

txt1 = 'Java'; txt2 = 'Python'
num1 = 5; num2 = 10

print('I like %s and %s!' %(txt1, txt2))
print('%s is %d times easier than %s.' %(txt2,num1,txt1))
print('%d + %d = %d' %(num1, num2, num1+num2))
print('Inflation rate in 2022: %d%%' %num1)

len()

msg = input('Insert a sentence.')
print(type(msg))
len = len(msg)                

print('The length of the sentence is ', len,'.')
print('The length of the sentence is {}.'.format(len))
print('The length of the sentence is %d.'%len)

count()

txt = 'A lot of things occur each day, every day.'

count1 = txt.count('o')            
count2 = txt.count('day')         
count3 = txt.count(' ')           

print('count1:', count1)
print('count2:', count2)
print('count3:', count3)

escape()

\n	enter
\t	tab
\\	print"\"
\'	print"'"
\"	print"""

print('I love Python.\n Python is easier than other languages!')
print('Name:John Simth\tSex:Male\tAge:22')
print('\"Welcome to Meadow\'s devlog!\"')
print('\'python\"')                
print('\\Java\\')

find()

txt = 'Today is Tuesday! I love Tuesdays.'

offset1 = txt.find('e')         # first 'e'
offset2 = txt.find('day')       # first 'day'
offset3 = txt.find('day', 20)   # 'day' after index[20]
offset4 = txt.find('j')         # no 'j' => returns -1

print('offset1:', offset1)		#11
print('offset2:', offset2)		#2
print('offset3:', offset3)		#29
print('offset4:', offset4)		#-1

 

strip()

txt = '    I am hungry!    '

result1 = txt.lstrip()  
result2 = txt.rstrip()
result3 = txt.strip()

print('<'+txt+'>')   #<    I am hungry!    >
print('<'+result1+'>')  #<I am hungry!    >
print('<'+result2+'>')  #<    I am hungry!>
print('<'+result3+'>') #<I am hungry!>

isdigit()

txt1 = '010-1234-5678'
txt2 = 'R2D2'
txt3 = '1212'

result1 = txt1.isdigit()
result2 = txt2.isdigit()
result3 = txt3.isdigit()

print('result1:', result1)          # False 
print('result2:', result2)          # False
print('result3:', result3)          # True