Table of contents
1. Example of Python Hello World
(3) We can also combine the above operations into one line of code:
(1) The square root, also called the quadratic root, is expressed as 〔√￣〕.
(3) Negative and complex numbers can be used in the following ways:
5. Python calculates the area of a triangle
6. Python calculates the area of a circle
Seven, Python random number generation
(1) In Python, you can use the built-in random module to generate random numbers.
Eight, Python Celsius temperature to Fahrenheit temperature
(1) The following example uses the user to input two variables and exchange them with each other:
(2) Do not use temporary variables
(2) We can also use the embedded if statement to achieve:
11. Python judges whether a string is a number
12. Python judges odd and even numbers
Fourteen, Python get the maximum value function
15. Python prime number judgment
16. Python outputs prime numbers within the specified range
Seventeen, Python factorial example
18. Python ninety-nine multiplication table
Nineteen, Python Fibonacci sequence
Twenty, Python Armstrong number
(2) Obtain the Armstrong number within the specified period
21. Python decimal to binary, octal, hexadecimal
(1) The following code is used to convert decimal to binary, octal, and hexadecimal:
(2) Example of binary conversion
(3) Example of octal conversion
(4) Example of hexadecimal conversion
Twenty-two, Python ASCII code and character conversion
23. Python greatest common divisor algorithm
24. Python Least Common Multiple Algorithm
Twenty-five, Python simple calculator implementation
Twenty-six, Python generates a calendar
Twenty-seven, Python uses recursive Fibonacci sequence
Thirty, Python string case conversion
31. Python calculates the number of days in each month
Thirty-two, Python gets yesterday's date
Thirty-three, Python list common operations
(3) Adding elements to the list
(7) Use the join link list to become a string
Thirty-four, Python Joseph living dead game
Thirty-six, Python realizes the stopwatch function
Thirty-seven, Python calculates the cubic sum of n natural numbers
Thirty-eight, Python calculates the sum of array elements
Thirty-nine, Python array flips the specified number of elements
(1) Define an integer array, and flip the specified number of elements to the end of the array.
(2) The following demonstrates placing the first two elements of the array behind the array.
1. Example of Python Hello World
The following example is the first example of learning Python, that is, how to output "Hello World!":
The output of executing the above code is:
Hello World！
Two, Python number summation
(1) The following example is to enter two numbers through the user and calculate the sum of the two numbers:
The output of executing the above code is:
Enter the first number: 1.5 Enter the second number: 2.5 The numbers 1.5 and 2.5 add up to: 4.0
In this example, we are summing two numbers entered by the user. The built-in function input() is used to get the user's input, and input() returns a string, so we need to use the float() method to convert the string to a number.
(2) Two digital operations, summing we use the plus (+) operator, in addition, there are minus (-), multiplication (*), division (/), floor division (//) or Take the remainder (%).
(3) We can also combine the above operations into one line of code:
The output of executing the above code is:
$ python test.py Enter the first number: 1.5 Enter the second number: 2.5 The sum of two numbers is 4.0
3. Python square root
(1) The square root, also called the quadratic root, is expressed as 〔√￣〕.
Such as: Mathematics language is: √￣16=4. The language description is: 16=4 under the root sign.
(2) The following example is to input a number by the user and calculate the square root of this number:
The output of executing the above code is:
$ python test.py Please enter a number: 4 The square root of 4.000 is 2.000
In this example, we take the user to enter a number and use the exponent operator ** to calculate the square root of that number.
The program only works with positive numbers.
(3) Negative and complex numbers can be used in the following ways:
The output of executing the above code is:
$ python test.py Please enter a number: -8 The square root of -8 is 0.000+2.828j
In this example, we use the sqrt() method of the cmath (complex math) module.
4. Python quadratic equation
The following example is to enter a number by the user and calculate the quadratic equation:
The output of executing the above code is:
$ python test.py Enter a: 1 Enter b: 5 Enter c: 6 The result is (-3+0j) and (-2+0j)
In this example, we use the sqrt() method of the cmath (complex math) module to calculate the square root.
5. Python calculates the area of a triangle
The following example is to calculate the area of the triangle by inputting the length of the three sides of the triangle by the user:
The output of executing the above code is:
$ python test.py Enter the length of the first side of the triangle: 5 Enter the length of the second side of the triangle: 6 Enter the length of the third side of the triangle: 7 The area of the triangle is 14.70
6. Python calculates the area of a circle
The formula for the area of a circle is:
In the formula r is the radius of the circle.
The output of the above example is:
The area of the circle is 78.550000
Seven, Python random number generation
(1) In Python, you can use the built-in random module to generate random numbers.
import random
(2) random. random()
random.random() returns a random decimal between 0.0 and 1.0
The output of executing the above code is:
0.7597072251250637
(3) random.randint(a, b)
random.randint(a, b) returns an integer between a and b (inclusive).
random.randint(a,b)
The function returns a number N, N is a number between a and b (a <= N <= b), including a and b.
The following example demonstrates how to generate a random number between 0 and 9:
The output of executing the above code is:
4
（四）random.choice(sequence)
random.choice(sequence) is used to randomly select an element from a sequence:
The output of executing the above code is:
4
（五）random.shuffle(sequence)
random.shuffle(sequence) is used to randomly sort the elements in the sequence:
The output of executing the above code is:
[3, 2, 4, 5, 1]
Eight, Python Celsius temperature to Fahrenheit temperature
The following example demonstrates how to convert Celsius to Fahrenheit:
The output of executing the above code is:
Enter temperature in Celsius: 38 38.0 Celsius to Fahrenheit is 100.4
In the above example, the formula for converting Celsius to Fahrenheit is celsius * 1.8 = fahrenheit - 32. So get the following formula:
centigrade = (Fahrenheit - 32) / 1.8
Nine, Python swap variables
(1) The following example uses the user to input two variables and exchange them with each other:
The output of executing the above code is:
Enter x value: 2 Enter y value: 3 The value of x after swapping is: 3 The value of y after swapping is: 2
In the above example, we created a temporary variable temp, and stored the value of x in the variable temp, then assigned the value of y to x, and finally assigned temp to the y variable.
(2) Do not use temporary variables
We can also swap variables in a very elegant way without creating temporary variables:
x,y = y,x
So the above example can be modified to:
The output of executing the above code is:
Enter x value: 1 Enter y value: 2 The value of x after swapping is: 2 The value of y after swapping is: 1
10. Python if statement
(1) The following example judges whether a number is positive, negative or zero by using the if...elif...else statement:
The output of executing the above code is:
Enter a number: 3 A positive number
(2) We can also use the embedded if statement to achieve:
The output of executing the above code is:
Enter a number: 0 zero
11. Python judges whether a string is a number
The following example determines whether a string is a number by creating a custom function is_number() method:
We can also do this with an inline if statement:
The output of executing the above code is:
False True True True True True True True False
more ways
The Python isdigit() method detects whether a string consists of digits only.
The Python isnumeric() method checks whether a string consists of numbers only. This method is only for unicode objects.
12. Python judges odd and even numbers
The following example is used to determine whether a number is odd or even:
We can also do this with an inline if statement:
The output of executing the above code is:
Enter a number: 3 3 is odd
13. Python judges leap year
The following example is used to determine whether the year entered by the user is a leap year:
We can also do this with an inline if statement:
The output of executing the above code is:
Enter a year: 2000 2000 is a leap year
Enter a year: 2011 2011 is not a leap year
Fourteen, Python get the maximum value function
In the following example we use the max() method to find the maximum value:
The output of executing the above code is:
2 b 2 2 80, 100, 1000 Maximum: 1000 -20, 100, 400 The maximum value is: 400 -80, -20, -10 The maximum value is: -10 0, 100, -400 Maximum value: 100
15. Python prime number judgment
A natural number greater than 1, except 1 and itself, cannot be divided by other natural numbers (prime numbers) (2, 3, 5, 7, etc.), in other words, the number has no other factors except 1 and itself .
The output of executing the above code is:
$ python3 test.py Please enter a number: 1 1 is not prime $ python3 test.py Please enter a number: 4 4 is not prime 2 times 2 is 4 $ python3 test.py Please enter a number: 5 5 is a prime number
16. Python outputs prime numbers within the specified range
Prime numbers (prime numbers), also known as prime numbers, are infinite. Not divisible by any divisor other than 1 and itself.
The following example can output prime numbers within the specified range:
Execute the above program, the output is:
$ python3 test.py Enter interval min: 1 Enter range max: 100 2 3 5 7 11 13 17 19 23 29 31 37 41 43 47 53 59 61 67 71 73 79 83 89 97
Seventeen, Python factorial example
The factorial of an integer (English: factorial) is the product of all positive integers less than or equal to the number, and the factorial of 0 is 1. Namely: n!=1×2×3×...×n.
The output of executing the above code is:
Please enter a number: 3 The factorial of 3 is 6
18. Python ninety-nine multiplication table
The following example demonstrates how to implement a nine-nine multiplication table:
The output of executing the above code is:
By specifying the value of the end parameter, you can cancel the output of the carriage return character at the end, so as not to wrap the line.
Nineteen, Python Fibonacci sequence
The Fibonacci sequence refers to such a sequence of 0, 1, 1, 2, 3, 5, 8, 13, especially pointing out that: the 0th item is 0, and the 1st item is the first 1. Starting with the third term, each term is equal to the sum of the previous two.
The code to implement the Fibonacci sequence in Python is as follows:
The output of executing the above code is:
How many items do you need? 10 Fibonacci sequence: 0 , 1 , 1 , 2 , 3 , 5 , 8 , 13 , 21 , 34 ,
Twenty, Python Armstrong number
If an n -digit positive integer is equal to the sum of the nth powers of its digits , the number is called an Armstrong number.
For example 1^3 + 5^3 + 3^3 = 153.
Armstrong numbers up to 1000: 1, 2, 3, 4, 5, 6, 7, 8, 9, 153, 370, 371, 407.
(1) The following code is used to detect whether the number entered by the user is an Armstrong number:
The output of executing the above code is:
$ python3 test.py Please enter a number: 345 345 is not an Armstrong number $ python3 test.py Please enter a number: 153 153 is the Armstrong number $ python3 test.py Please enter a number: 1634 1634 is the Armstrong number
(2) Obtain the Armstrong number within the specified period
The output of executing the above code is:
Min: 1 Maximum value: 10000 1 2 3 4 5 6 7 8 9 153 370 371 407 1634 8208 9474
In the above example we output the Armstrong numbers between 1 and 10000.
21. Python decimal to binary, octal, hexadecimal
(1) The following code is used to convert decimal to binary, octal, and hexadecimal:
The output of executing the above code is:
python3 test.py Enter number: 5 The decimal number is: 5 Converted to binary as: 0b101 Converted to octal is: 0o5 Converted to hexadecimal: 0x5
(2) Example of binary conversion
Output result:
Binary number: 101010 Convert to decimal: 42 Convert to octal: 0o52 Convert to hex: 0x2a
(3) Example of octal conversion
Output result:
Octal number: 52 Convert to decimal: 42 Converted to binary: 0b101010 Convert to hex: 0x2a
(4) Example of hexadecimal conversion
Output result:
Hexadecimal number: 2a Convert to decimal: 42 Converted to binary: 0b101010 Convert to octal: 0o52
Twenty-two, Python ASCII code and character conversion
The following codes are used to convert between ASCII codes and characters:
The output of executing the above code is:
python3 test.py Please enter a character: a Please enter an ASCII code: 101 The ASCII code of a is 97 101 corresponds to the character e
23. Python greatest common divisor algorithm
The following code is used to implement the greatest common divisor algorithm:
The output of executing the above code is:
Enter the first number: 54 Enter the second number: 24 The greatest common divisor of 54 and 24 is 6
24. Python Least Common Multiple Algorithm
The following code is used to implement the least common multiple algorithm:
The output of executing the above code is:
Enter the first number: 54 Enter the second number: 24 The least common multiple of 54 and 24 is 216
Twenty-five, Python simple calculator implementation
The following code is used to implement a simple calculator, including basic addition, subtraction, multiplication and division of two numbers:
The output of executing the above code is:
Select operation: 1. Add 2. Subtraction 3. Multiply 4. Divide Enter your choice (1/2/3/4): 2 Enter the first number: 5 Enter the second number: 2 5 - 2 = 3
Twenty-six, Python generates a calendar
The following code is used to generate a calendar for a specified date:
The output of executing the above code is:
Enter year: 2015
Enter month: 6
June 2015
Mon Tu We Th Fr Sa Su
1 2 3 4 5 6 7
8 9 10 11 12 13 14
15 16 17 18 19 20 21
22 23 24 25 26 27 28
29 30
Twenty-seven, Python uses recursive Fibonacci sequence
The following code uses recursion to generate the Fibonacci sequence:
The output of executing the above code is:
How many items do you want to output? 10 Fibonacci sequence: 0 1 1 2 3 5 8 13 21 34
28. Python file IO
The following code demonstrates Python's basic file operations, including open, read, and write:
The output of executing the above code is:
This text will be written to the file See me now!
29. Python string judgment
The following code demonstrates the judgment of Python strings:
The output of executing the above code is:
Test case one False False False True False False False ------------------------ Test case two True True False True False False
Thirty, Python string case conversion
The following code demonstrates how to convert a string to uppercase, or convert a string to lowercase, etc.:
# Filename : test.py # author by : www.runoob.com str = "www.runoob.com" print(str.upper()) # Convert lowercase letters in all characters to uppercase letters print(str.lower()) # Convert uppercase letters in all characters to lowercase letters print(str.capitalize()) # Convert the first letter to uppercase and the rest to lowercase print(str.title()) # Convert the first letter of each word to uppercase, and the rest to lowercase
The output of executing the above code is:
WWW.RUNOOB.COM www.runoob.com Www.runoob.com Www.Runoob.Com
31. Python calculates the number of days in each month
The following code calculates the number of days in a month by importing the calendar module:
The output of executing the above code is:
(3, 30)
The output is a tuple, the first element is the day of the week (0-6) corresponding to the first day of the month being checked, and the second element is the number of days in the month. The output of the above example means that the first day of September 2016 is Thursday, and there are 30 days in total in this month.
Thirty-two, Python gets yesterday's date
The following code gets yesterday's date by importing the datetime module:
The output of executing the above code is:
2023-07-01
The above example output means that yesterday's date is July 1, 2023.
Thirty-three, Python list common operations
(1) list definition
>>> li = ["a", "b", "mpilgrim", "z", "example"]
>>> li
['a', 'b', 'mpilgrim', 'z', 'example']
>>> li[1]
'b'
(2) list negative index
>>> li
['a', 'b', 'mpilgrim', 'z', 'example']
>>> li[-1]
'example'
>>> li[-3]
'mpilgrim'
>>> li
['a', 'b', 'mpilgrim', 'z', 'example']
>>> li[1:3]
['b', 'mpilgrim']
>>> li[1:-1]
['b', 'mpilgrim', 'z']
>>> li[0:3]
['a', 'b', 'mpilgrim']
(3) Adding elements to the list
>>> li
['a', 'b', 'mpilgrim', 'z', 'example']
>>> li.append("new")
>>> li
['a', 'b', 'mpilgrim', 'z', 'example', 'new']
>>> li.insert(2, "new")
>>> li
['a', 'b', 'new', 'mpilgrim', 'z', 'example', 'new']
>>> li.extend(["two", "elements"])
>>> li
['a', 'b', 'new', 'mpilgrim', 'z', 'example', 'new', 'two', 'elements']
(4) list search
>>> li
['a', 'b', 'new', 'mpilgrim', 'z', 'example', 'new', 'two', 'elements']
>>> li.index("example")
5
>>> li.index("new")
2
>>> li.index("c")
Traceback (innermost last):
File "<interactive input>", line 1, in ?
ValueError: list.index(x): x not in list
>>> "c" in li
False
(5) list delete elements
list.remove(x): x not in list >>> li.pop() # pop will do two things: remove the last element of the list, and then return the value of the removed element. 'elements' >>> li ['a', 'b', 'mpilgrim', 'example', 'new', 'two']
(6) list operator
>>> li = ['a', 'b', 'mpilgrim']
>>> li = li + ['example', 'new']
>>> li
['a', 'b', 'mpilgrim', 'example', 'new']
>>> li += ['two']
>>> li
['a', 'b', 'mpilgrim', 'example', 'new', 'two']
>>> li = [1, 2] * 3
>>> li
[1, 2, 1, 2, 1, 2]
(7) Use the join link list to become a string
>>> params = {"server":"mpilgrim", "database":"master", "uid":"sa", "pwd":"secret"}
>>> ["%s=%s" % (k, v) for k, v in params.items()]
['server=mpilgrim', 'uid=sa', 'database=master', 'pwd=secret']
>>> ";".join(["%s=%s" % (k, v) for k, v in params.items()])
'server=mpilgrim;uid=sa;database=master;pwd=secret'
join can only be used on lists whose elements are strings; it does not perform any type coercion. Concatenating a list with one or more non-string elements will raise an exception.
(8) list split string
>>> li = ['server=mpilgrim', 'uid=sa', 'database=master', 'pwd=secret']
>>> s = ";".join(li)
>>> s
'server=mpilgrim;uid=sa;database=master;pwd=secret'
>>> s.split(";")
['server=mpilgrim', 'uid=sa', 'database=master', 'pwd=secret']
>>> s.split(";", 1)
['server=mpilgrim', 'uid=sa;database=master;pwd=secret']
split is the opposite of join, it splits a string into a multi-element list.
Note that the separator (";") is completely removed, it does not appear in any elements of the returned list.
split accepts an optional second argument which is the number of times to split.
(9) Mapping analysis of list
>>> li = [1, 9, 8, 4]
>>> [elem*2 for elem in li]
[2, 18, 16, 8]
>>> li
[1, 9, 8, 4]
>>> li = [elem*2 for elem in li]
>>> li
[2, 18, 16, 8]
(10) Analysis in dictionary
>>> params = {"server":"mpilgrim", "database":"master", "uid":"sa", "pwd":"secret"}
>>> params.keys()
dict_keys(['server', 'database', 'uid', 'pwd'])
>>> params.values()
dict_values(['mpilgrim', 'master', 'sa', 'secret'])
>>> params.items()
dict_items([('server', 'mpilgrim'), ('database', 'master'), ('uid', 'sa'), ('pwd', 'secret')])
>>> [k for k, v in params.items()]
['server', 'database', 'uid', 'pwd']
>>> [v for k, v in params.items()]
['mpilgrim', 'master', 'sa', 'secret']
>>> ["%s=%s" % (k, v) for k, v in params.items()]
['server=mpilgrim', 'database=master', 'uid=sa', 'pwd=secret']
(11) list filter
>>> li = ["a", "mpilgrim", "foo", "b", "c", "b", "d", "d"]
>>> [elem for elem in li if len(elem) > 1]
['mpilgrim', 'foo']
>>> [elem for elem in li if elem != "b"]
['a', 'mpilgrim', 'foo', 'c', 'd', 'd']
>>> [elem for elem in li if li.count(elem) == 1]
['a', 'mpilgrim', 'foo', 'c']
Thirty-four, Python Joseph living dead game
30 people on a boat, overloaded, need 15 people to disembark.
So people line up in a line, and the position in line is their number.
Counting starts from 1 and people who count to 9 disembark.
This cycle continues until there are only 15 people left on the boat. Which numbered people have disembarked?
Execute the above example, the output result is:
No. 9 disembarked disembarked on the 18th disembarked on the 27th No. 6 disembarked disembarked on the 16th disembarked on the 26th No. 7 disembarked disembarked on the 19th Disembarked on the 30th Disembarked on the 12th disembarked on the 24th No. 8 disembarked disembarked on the 22nd No. 5 disembarked disembarked on the 23rd
Thirty-five, Python five fish
Five people A, B, C, D, and E went fishing together one night, and they were all exhausted in the early morning of the next day, so they each found a place to sleep.
There are three shots in the day, A wakes up first, he divides the fish into five parts, throws away the extra fish, and takes his own part.
B wakes up the second time, also divides the fish into five parts, throws away the extra fish and takes his own part. .
C, D, and E wake up in turn and take the fish in the same way.
How many fish did they catch at least?
operation result:
There are 3121 fish in total
Thirty-six, Python realizes the stopwatch function
The following example uses the time module to implement the stopwatch function:
The test results are:
Press Enter to start timing, and Ctrl + C to stop timing. start Timing: 3.0 seconds Timing: 5.0 seconds ^C end 6.0 seconds Total time: 6.69 secs
Thirty-seven, Python calculates the cubic sum of n natural numbers
Calculation formula 13 + 23 + 33 + 43 + .... + n3
Implementation requirements:
Input: n = 5
output: 225
Formula: 13 + 23 + 33 + 43 + 53 = 225
Input: n = 7
Input: 784
Formula: 13 + 23 + 33 + 43 + 53 + 63 + 73 = 784
The output of the above example is:
225
Thirty-eight, Python calculates the sum of array elements
Define an array of integers and calculate the sum of the elements.
Implementation requirements:
Input: arr[] = {1, 2, 3}
output: 6
Calculation: 1 + 2 + 3 = 6
The output of the above example is:
The sum of the array elements is 34
Thirty-nine, Python array flips the specified number of elements
(1) Define an integer array, and flip the specified number of elements to the end of the array.
For example: (ar[], d, n) flips the first d elements of the array arr with length n to the end of the array.
(2) The following demonstrates placing the first two elements of the array behind the array.
Raw array:
After flipping:
(3) Example 1
The output of the above example is:
3 4 5 6 7 1 2
(4) Example 2
The output of the above example is:
3 4 5 6 7 1 2
(5) Example 3
The output of the above example is:
3 4 5 6 7 1 2