2020 New Year's learning python

Efficiency good low today (I love butt, whatever the outcome today after all the gold climb hhh)

To sum up what it learned today

+	plus
-	Less
*	Multiply
/	except
//	Divisible (take quotient)
%	Remainder
**	Index (X = X ** Y ^Y )

1, it can be used to connect the plurality of strings +

2、

% S indicates the character string,

% D represents an integer before the integer spaces can be written as% 5d% 123 will be denoted by "123" accounted for five character positions

% F% 4.2f floating point format to a format, the total length of 4, 2 represents two decimal places

3、

1 a='This is {0:s} {1:d}st python program.'.format ('Max', 1)
2 
3 print(a)

4. List

userAge=[21,22,23,24,25]

A = userAge [0] # remove the 0-th element 

B = userAge [2:. 4] # removed [2,4) always left and right open and closed 

C = userAge [. 1:. 5: 2] # removed [1,5) step 2

# Modify elements directly 

userAge [ . 1] =. 5

d=userAge

# Add the last element using the append () function 

userAge.append ( 99 )

e=userAge

# Remove elements

del userAge[2]

f=userAge

print(a)

print(b)

print(c)

print(d)

print (e)

print(f)

5-tuple

But much like the list with () do not []. Also you can not modify the value tuples

6, dictionary

use{}

= {userNameAndAge " Peter " : 38 is, " Max " : 18 is, " the Dell " :}. 19 # dict may or may not declare Dictionary

#写成userNameAndAge=dict(Peter=38,Max=18,Dell=19)

a=userNameAndAge["Peter"]

print(a)

userNameAndAge [ " Peter " ] = 39 # modify dictionary

del userNameAndAge [ " Peter " ] # Delete Peter option

7, interactive program: Input, print

myName=input("Please enter ur name")
print("Hello World, my name is ",myName)

8, multi-line expansion: Three quotes

print('''Hello World
My name is Max and
I love Dell.
''')

9, escaped

\ N print a new line

\ T Tab

10, if conditions

①If condition 1 is met：

do A

elif #else if condition 2 is met:

do B

Relying tab python program to determine the starting position

②do Task A if condition is true else do Task

num1=12 if myInt==10 else 13

11, for circulation

= Qucik Facts Pets [ ' CATS ' , ' Dogs ' , ' Rabbits ' ]
 for index, myPets in the enumerate (Qucik Facts Pets): # the enumerate to display the index values in the list && do not forget: this stuff 
        Print (index, myPets)

12, while cycling

While condition is true：

do A

counter=5
while counter>0:
    print("Counter = ", counter)
    counter=counter-1

Break usage will not go

Continue keyword after the procedure will be skipped in this cycle

j=0
for i in range(5):
    j=j+2
    print('\ni = ', i, ', j = ', j)
    if j==6:
        continue
    print('I will be skipped over if j=6')

13、try &except

try :

do something

except:

do something else when an error occurs.

try:
    answer =12/0
    print(answer)
except:
    print("An error occured")

2020 New Year's learning python

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