Python road, Python basics 2 (second week)

One,. PYc is what a ghost:

PYC files are actually a persistent way to save Pycodeobject.

Ii. Types of data

1. number:

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 a mathematical representation of a complex number?

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

#复数, the production environment is used relatively little.

Python 2.7 has integral and long integer types:

>>> (2)-1

1

>>> (2**31)-1

2147483647L

>>>

>>> type ((2**30)-1)

<type ' int ' >

>>> type ((2**31)-1)

<type ' Long ' >

>>>

Python 3.x does not have integral and long integer types:

>>> type ((2**30)-1)

<class ' int ' >

>>> type ((2**31)-1)

<class ' int ' >

>>>

2. Boolean value

True or False

1 or 0

>>> 1 is True

False

>>> 0 is False

False

>>> 0 is True

False

3. string

"hello world"

string concatenation of all Evils:

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 Evil + sign will re-open up a space within each occurrence.

>>> name = ' Luchuan '

>>> Print ("my name is" + name + "and You?")

My name is Luchuan and you?

>>>

#这等于三块内存空间

String formatted output

Name = "luchuan"

Print "i am%s"% name

#输出: I am Luchuan

PS: string is%s; integer%d; floating-point number%f

String Common Functions:

Remove whitespace

Segmentation

Length

Index

Slice

1) Strip Remove Blank

Username = input ("user:")

If username.strip () = = ' Alex ':

Print ("welcome")

2) Split Split

Name = "alex,jack,rain"

name2 = Name.split (",")

Print (name2)

3) Join string together

Name = "alex,jack,rain"

name2 = Name.split (",")

Print ("|". Join (NAME2))

4) "in name to determine if there are no spaces

Name= "alex li"

Print ("in Name")

5) Capitalize first Letter capital

Name= "alex li"

Print (name.capitalize ())

6) Format formatted

msg = "Hello, {name}, It ' s been a long {age} since last time Sopke ..."

MSG2 = Msg.format (name= ' xiaoming ', age=33)

Print (msg2)

MSG2 = "haha{0}, dddd{1}"

Print (msg2.format (' Alex ', 33))

7) Center Center

Name= "alex li"

Print (name.center (40, '-'))

8) Find Lookup

name = ' ALEX3SDF '

Print (name.find (' a '))

9) whether the isdigit is a digital

Age = Input ("your Age:")

If Age.isdigit ():

age = int (age)

Print (age)

Else

Print ("invalid Data Type")

Isalnum If only alphanumeric characters are included

name = ' ALEX3SDF '

Print (name.isalnum ())

One) EndsWith when does the end

name = ' ALEX3SDF '

Print (name.endswith (' DF '))

StartsWith when does it start?

name = ' ALEX3SDF '

Print (name.startswith (' DF '))

Upper Caps

name = ' ALEX3SDF '

Print (name.upper ())

) Lower lowercase

name = ' ALEX3SDF '

Print (name.upper (). Lower ())

Len length

Print (len (name))

4. List

Lists are called in Python only, and are called arrays in other Languages.

To create a list:

Name_list = [' Alex ', ' seven ', ' Eric ']

Or

name_list = list ([' Alex ', ' seven ', ' Eric ')

Basic Operation:

Index

Slice

Additional

Delete

Length

Cycle

Contains

Name = [' Alex ', ' Jack ', ' Rain ', ' Eric ', ' Monica ', ' Fiona ']

>>> name[:]

[' Alex ', ' Jack ', ' Rain ', ' Eric ', ' Monica ', ' Fiona ']

Index

>>> name[2]

' Rain '

Slice

>>> name[2:4]

[' Rain ', ' Eric ']

>>> name[2:4][0]

' Rain '

>>> name[2:4][0][1:2]

A

Modify:

>>> name[1]= "xiaoming"

>>> Name

[' Alex ', ' xiaoming ', ' Rain ', ' Eric ', ' Monica ', ' Fiona ']

Insert:

>>> name.insert (2, ' daming ')

>>> Name

[' Alex ', ' xiaoming ', ' daming ', ' Rain ', ' Eric ', ' Monica ', ' Fiona ']

Additional:

>>> name.append (' Alex ')

>>> Name

[' Alex ', ' xiaoming ', ' daming ', ' Rain ', ' Eric ', ' Monica ', ' Fiona ', ' Alex ']

Delete:

>>> Name.remove ("daming")

>>> Name

[' Alex ', ' xiaoming ', ' Rain ', ' Eric ', ' Monica ', ' Fiona ', ' Alex ']

Practice:

Insert the name of two pro group members into the middle

List of people taking out 第3-8

Delete a 9th person

Delete the 2 other groups that you just joined, one at a time.

Add the Leader's name to the group Leader's notes

Ask you to print a person every other person

>>> name = [' Alex ', ' xiaoming ', ' Rain ', ' Eric ', ' Monica ', ' Fiona ']

>>> Name.insert ( -1, "xiaochuan")

>>> Name.insert (5, "dachuan")

>>> name[3:8]

[' Eric ', ' Monica ', ' Dachuan ', ' Xiaochuan ', ' Fiona ']

>>> Name.remove ("Fiona")

>>> Name

[' Alex ', ' xiaoming ', ' Rain ', ' Eric ', ' Monica ', ' Dachuan ', ' Fiona ']

>>> del name[4:6]

>>> Print (name[::2])

Length:

>>> Len (name)

7

>>> Name

[' Alex ', ' xiaoming ', ' Rain ', ' Eric ', ' Monica ', ' Fiona ', ' Alex ']

5, tuples (immutable List)

To create a tuple:

ages = (11, 22, 33, 44, 55)

Or

ages = tuple ((11, 22, 33, 44, 55))

6. Dictionary (unordered)

To create a dictionary:

person = {"name": "mr.wu", ' Age ': 18}

Or

person = dict ({"name": "mr.wu", ' age ': 18})

Common Operations:

Index

New

Delete

key, value, Key-value Pairs

Cycle

Length

third, Data operation

The smallest unit that can be represented in a computer is a bits.

The smallest unit that can be stored in a computer is a bits (bit).

8bit = byte (bytes)

1024byte = 1kbyte

1024kbyte = 1mbyte

1024MB = 1GB

1024GB = 1T

Arithmetic operations:

Comparison Operation:

Assignment operation:

Logical operation:

Member Operations:

Identity operation:

Bit operations:

This article is from the "curves" blog, so be sure to keep this source http://luchuangao.blog.51cto.com/11311715/1852009

Python road, Python basics 2 (second week)