Python2.7 Basic Syntax

1. Keywords

The Python standard library provides the keyword module, which can output all the keywords for the current version:

>>>Importkeyword>>>keyword.kwlist[' and',' as','assert',' Break','class','Continue','def','del','elif','Else','except','exec','finally',' for',' from','Global','if','Import','inch',' is','Lambda',' not','or','Pass','Print','Raise','return','Try',' while',' with','yield']>>>

2. Notes:

Single-line comment with #, multiline comment with "' or" "

3. Variables:

Variables in Python do not need to be declared. Each variable must be assigned before it is used, and the variable will be created after the variable is assigned.

• Python can assign values to multiple variables at the same time, such as a, B = 1, 2.
• The Numeric division (/) always returns a floating-point number to get the integer using the//operator.
• A variable can point to different types of objects by assigning values.
• In mixed calculations, Python converts an integer to a floating-point number

4. String:

The string str in Python is enclosed in single quotation marks (') or double quotation marks ("").

Escape special characters with backslash (\)

Strings can be concatenated with the + operator string, or repeated with the * operator

>>> text='ice'+'  cream'print(text) Ice cream>>> text='ice cream'print(text) ice Creamice Creamice Cream

Use three quotation marks ("..." or "" "..." ") to specify a multiline string

" " AAABBBCCC " " Print (text) AAABBBCCC

>>> text='iccecream'print(text) Iccecream

If you do not want the backslash to escape, you can add an R or R before the string to represent the original string.

>>> Text1 = r'E:\notice'print  text1e:\notice

The

Python string cannot be changed. Assigning a value to an index position causes an error

>>> text='ice cream'>>> text[0]='t'  Traceback (most recent):  '<pyshell#117>' in < Module>    text[0]='t'str '  not support item assignment

5: Three mesh operator

if Else y Print (z)

6. Branch

 whileTrue:score= Int (Input ("Please input your score:"))    if<= Score <= 100:        Print('A')    elifScore >= 80:        Print('B')    elifScore >= 70:        Print('C')    elifScore >= 60:        Print('D')    Else:        Print('Your score is too low')

7. Cycle

The general format for the For loop is as follows:

For <variable> in <sequence>:

<statements>

Else

<statements>

>>> Languaegs = ['C','C + +','Java','python']>>> forLanguageinchLanguaegs:Print(language, Len (language)) ('C', 1)('C + +', 3)('Java', 4)('python', 6)>>>

A looping statement can have an ELSE clause

 forNuminchRange (2, 10):     forXinchRange (2, num):ifnum%x = =0:Print(Num,'equals'X'*', num//x) Break    Else:        #no element found in loop        Print(Num,'Is a prime number')

Cond...

Python2.7 Basic Syntax