python learn D3

Introduction to basic types

2.1 Numeric int.

Numbers are mainly used for calculation, and there are not many ways to use them, just remember one:

2.2 String str stores a small amount of data

'alex' ,'1235443543'

'[1,2,3]'

3.3 Boolean value bool

True False

4.4 List List data of various data types, a large amount of data, easy to operate.

['name',True,[]....],

5.5 tupe read-only list

Use () to represent (1, 2, 3)

6.6 Dictionary dict stores a large amount of data, relational data. Store data in the form of key-value pairs

{'name':'old boy',

'name_list':['Reverse teaching material',.....]

'alex':{'age':40,

'hobby':'old_women',

}

7.7 set

{'wusir', 'alex', ....}

specific usage

int

#i = 100

#print（i.bit_length()）

Convert decimal to binary significand

1 0000 0001

2 0000 0010

3 0000 0011

100

bool

int <---> str mutual conversion

str ---> int int(str) Condition: The string must consist of all numbers.

# age = int(input('>>>'))

# print(age,type(age))

int ---> str str(int)

# s1 = str (123)

#s2 = 123

# print(s1, type(s1))

# print(s2, type(s2))

bool <---> int

bool ---> int True --->1 False ---> 0

# print(int(True))

# print(int(False))

int ---> bool non-zero is True, zero is False.

# print(bool(100))

# print(bool(-1))

# print(bool(0))

str

  i ='python 12th term'

index

Counting from 0 in order 0 . 1. 2...

From right to left is -1 -2 -3 .....

# i1 = i[0]
# print(i1)
# i2 = i[4]
# print(i2)
# i3 =i[-1]
# print(i3)

slice

(regardless of the head and the butt)

# i4 = i [0: 6] 
# print (i4) 
# i5 = i [: 6] 
# print (i5) python 
# i6 = i [1: 4] 
# print (i6) yth 
# i7 = i [5: ] 
# print (i7) n12 期
# i8 = i [:] 
# print (i8) python12 期

step size

# i9 = i[:5:2] The empty space in front is the beginning of the beginning to 5, the step size is 2 
# print(i9) pto 
# i10 = i[4::2] The middle space is the end, the step size is 2 from 4 to the end 
# print(i10) o1 period 
# i11 = i[-1:-5:-1] back-to-front step is 1 
# print(i11) period 21n 
# i12 = i[-3:-1] slice from -3 to -2 (regardless of head and tail) 
# print(i12) 12

Common operations on strings

s = 'laoNANhai'

** capitalize Capitalize the first letter and lowercase the rest.

# s1 = s.capitalize()
# print(s1)           # Laonanhai

* center is centered. The first parameter determines the size, * means to fill the left and right empty parts

# s2 = s.center(15,"*")
# print(s2)          #***laoNANhai***

*** upper all uppercase

lower all lowercase

# s3 = s.upper() 
# s31 er() 
# print(s3) LAONANHAI 
# print(s31) laonanhai

# code = 'QAdr'.upper() 
# your_code = input('Please enter the verification code, case insensitive:').upper() 
# if your_code == code: 
# print('Verification successful')

*** startswith : Determine what content to start with, return bool, can be sliced, used for slices, separated

endswith ：

startswith(self, prefix, start=None, end=None)

# s4 = s.startswith('l')
# s41 = s.startswith('lao')
# s42 = s.startswith('N', 3, 6)
# print(s42)        True
# print(s4)          True
# print(s41)        False

* swapcase : case flip

# s5 = s.swapcase()
# print(s5)

* title : Capitalize the first letter of each non-letter-separated word

# ss = 'gdsj wusir6taibai*ritian'
# s6 = ss.title()
# print(s6)

*** index : Find the index through the element, it can be sliced, and no error will be reported.

*** find : find the index by element, it can be sliced, if not found, return -1

# s7 = s.find('a') 
# s71 = s.find('A',2,) 2 Find from the second 
# s71 = s.find('Q',) 
# print(s71) 
# s72 = s.index('Q') 
# print(s72) 
# print(s71) 
# ss = '\talex\n' 
# print(ss)

*** strip removes leading and trailing spaces, newlines \n, tabs (tab key \t)

You can also remove the specified characters before and after (must be in the order of appearance)

# ss = 'ablabsexsba' 
# s9 = ss.strip('a') 
# s9 = ss.strip('abs') 
# lstrip() strips from the left    
# rstrip() strips from the right 
# print(s9)

ps prevents users from swiping to enter spaces or other whitespace characters

username = input( ' Please enter your username ' ).strip()
 if username == ' Wanrong ' :
 print ( ' Login successful ' )

*** split str ---> list

Separated by spaces by default

# s = 'wusir alex taibai' 
# st = 'wusir,alex,taibai' 
# st1 = 'QwusirQalexQtaibai' 
# s10 = s.split() 
# print(s10) 
# s101 = st.split(',') 
# print (s101) 
# s102 = st1.split('Q',2) 2 means the first two Q's to split 
# print(s102)

*** join list ---> str in some cases

# s = 'alex'
# s11 = '+'.join(s)
# print(s11)
# l = ['wusir', 'alex', 'taibai']
# s111 = ' '.join(l)
# print(s111,type(s111))

**repalce replace the specified character

replace(self, old, new, count=None)

# s = 'small pink tender little pink tender ghlasdfg small pink tender' 
# # s12 = s.replace('small pink tender', 'big hammer') 
# s12 = s.replace('small pink tender', 'large Hammer', 2) The number 2 means to replace only the first two characters 
# print(s12)

public method

s = 'fdsajlskgjdsaf;jdskfsdaf'

len() total number

# print(len(s))

count ('') counts the number of occurrences of certain elements, which can be sliced

 # c1 = s.count('f')
   # print(c1)

format formatted output

three ways

# msg = 'My name is {}, this year {}, my hobby {}'.format('Taibai', '20', 'girl') 
# print(msg)

# msg = 'My name is {0}, this year is {1}, my hobby is {2}, my name is still {0}'.format('Taibai', '20', 'girl') 
# print(msg)

# msg = 'My name is {name}, this year is {age}, and my hobby is {hobby}'.\ 
# format(name='Taibai', hobby='girl', age='20') 
# print(msg)

Judge sentences

# name='jinxin123' 
# print(name.isalnum()) #The string consists of letters or numbers True 
# print(name.isalpha()) #The string consists of only letters False 
# print(name.isdigit()) # string only consists of numbers False

2.1 Numeric int.

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