Python Learning Note 2

Pycharm the Use

IDE (Integrated Development Environ ment): Integrated development Environment

Vim: A classic Linux text editor (Novice and great gods like to use)

The Emacs:linux text editor is easier to use than vim.

Eclipse:java IDE, also supports python,c,c++

Visual Studio: IDE developed by Microsoft, supports python,c++,java,c#

notepad++: Python Support

Developed by Sublim:python

Pycharm: IDE primarily for python development

Show Toolbars:

Set the main interface font size

Run

Set automatically generate author and time

(English-Chinese word translation

Interpreter: Interpreter (translator) Toolbar: Toolbar Salary: Payroll Location: Position Untitled: Unnamed Fullstack: Full stack (can do anything)

CTRL +? : Press the shortcut key----"Full comment" when all is selected)

Character formatting output

PLACEHOLDER:

%s: Representing string%d: representing integer%f: floating-point number

The result is:

Data type initial:

1. Digital

　　2 is an example of an integer.
Long integers are just larger integers.
3.23 and 52.3E-4 are examples of floating-point numbers. The e tag represents a power of 10. Here, 52.3E-4 means 52.3 * 10-4.
( -5+4j) and (2.3-4.6j) are examples of complex numbers, where -5,4 is a real number, j is an imaginary number, and what is the plural in mathematics?

int (integral type)

On a 32-bit machine, the number of integers is 32 bits and the value range is -2**31~2**31-1, which is -2147483648~2147483647
On a 64-bit system, the number of integers is 64 bits and the value range is -2**63~2**63-1, which is -9223372036854775808~9223372036854775807

Long (integer)
Unlike the C language, Python's long integers do not refer to the positioning width, that is, Python does not limit the size of long integer values, but in fact, because of limited machine memory, we use a long integer value can not be infinite.
Note that, since Python2.2, Python automatically converts integer data to long integers if an integer overflows, so it does not cause any serious consequences if you do not add the letter L after long integer data.
Float (float type)
A floating-point number is used to process real numbers, which are numbers with decimals. Similar to the double type in C, accounting for 8 bytes (64 bits), where 52 bits represent the bottom, 11 bits represent the exponent, and the remaining one represents the symbol.
Complex (plural)
The complex number consists of real and imaginary parts, the general form is X+yj, where x is the real part of the complex, and Y is the imaginary part of the complex, where x and y are real numbers.

Note: Small number pools exist in Python:-5 ~ 257

2. Boolean value

True or False

Ture or False

1 or 0

3. String

"Hello World"

A string enclosed in single quotation marks ' or double quotation marks '.

Single and double quotes are basically no different, the only thing to note is that single and double quotation marks are separated by "'" or "" in a string.

The corresponding operation of the string

1.print (' hello ') print two times for Hello

2. Get the string by index, same as the slice operation of the list

Print (' Hello ' [2:]) Prints the result to Llo

3.print (' 0 ' in ' hello ') determines whether the content is printed in a string with a Boolean value of Ture or False

4. Formatting strings

Print ('%s is a good teacher '% ' Alex ') prints the result: Alex is a good teacher

5. String concatenation:

The string in Python is represented in the C language as a character array, and each time a string is created, it needs to open a contiguous space in memory, and once you need to modify the string, you need to make room again, and the + sign will re-open a space within it each time it appears.

A= ' 123 '

b= ' abc '

C=a+b

Print C

A/b variable, generating a new variable c = ' 123abc '

　　

C= '. Join ([A, b]) print (c) Join as a string built-in method

6.python--The built-in method of the string (Python is already written, call directly)# print (S.center (50, ' # ')) # Center

Print (St.count (' L ')): Number of statistical elements

Print (St.capitalize ()): Capitalize first letter

Print (St.center (50, ' # ')): Centered

Print (St.endswith (' Tty3 ')): Determines whether to end with a certain content

Print (St.startswith (' he ')): Determines whether to start with a content

Print (St.expandtabs (tabsize=20)): Tab key relationship to space bar

Print (St.find (' t ')): finds the first element and returns the index value

Print (St.format (name= ' Alex ', age=37)): Another way to format the output

Print (St.format_map ({' name ': ' Alex ', ' age ': 22})): Same as above, except input parameters are different

Print (St.index (' t ')): Find index value, no error found

Print (' ASD '. Isalnum ()): Determines whether a combination of numbers and letters (kanji can)

Print (' 12632178 '. Isdecimal ()): Determines whether it is a decimal number

Print (' 1269999.uuuu '. IsNumeric ()): Determines whether a number

Print (' abc '. isidentifier ()): Determines whether illegal characters

Print (' ABC '. Islower ()): Determines if all lowercase

Print (' ABC '. Isupper ()): Determines whether all uppercase

Print (' E '. isspace ()): Determines whether it is empty

Print (' My title '. Istitle ()): Determines whether it is like a title (capitalized in the first letter of each word)

Print (' My tltle '. Lower ()): Uppercase to lowercase

Print (' My tltle '. Upper ()): Lowercase to uppercase

Print (' My tltle '. Swapcase ()): uppercase to lowercase, lowercase to uppercase

Print (' My tltle '. Ljust (50, ' * ')): output string Left

Print (' My tltle '. Rjust (50, ' * ')): Right

Print (' \tmy tltle\n '. Strip ()): Remove front and back invisible (spaces, line breaks, tabs)

Print (' \tmy tltle\n '. Lstrip ()): Remove left invisible

Print (' My title title '. Replace (' itle ', ' lesson ', 1) '): replace (1 is the number of replacements)

Print (' My title title '. RFind (' t ')): Search from right to left, index value unchanged

Print (' My title title '. Split (' I ', 1) '): Split, splits the string into a list (joins the list composition string)

Print (' My title title '. Title ()): Capitalize first letter

Loops (Loop)

Limited cycles: Number of times limit------for loop for a finite loop

Infinite loop: = Dead loop

For loop

For I in range ()

I is a custom variable

Range () can be replaced with a list, a tuple

Flag bit

Break and Continue

List

Increase

A.append () Add value of content (default tea as to last position)

A.insert (Index, "content") index is indexed, subscript

By deleting

A.remove ("content") List-in-value method

A.pop (index) based on so deleted, the deleted value can be returned

Del A[index] del A can delete a variable (object) directly

A.clear () empty

Change

a[index]= "New value" a[index1,index2]=["," "

Check

Slice:

Print (A[1:3]) gets the second and third values

Print (A[1:3:1]) is taken from left to right, and the last 1 represents the step

Print (A[1:-1]) takes the second-to-last value

Print (A[1::-1]) from right to left

A.count () query the number of occurrences of an element by using the Count method

A.index () find element position by index (find location by content)

Sort

A.sort () sort from small to large

A.reverse () Reverse

Identity judgment

Is

Type (a) is List

Python Learning Note 2