What does the sign mean in Python

 

Brief overview of programming with Python


Data types

Integer

i = 1

Integer

Float

f = 0.1

Floating point number

String

s = "Hello"

String

list

l = [1, 2, 3]

Changeable list with order

Tuple

t = (1, 2, 3)

Unchangeable list with sequence

Dictionary

d = {1: "one", 2: "two", 3: "three"}

Associative array

Conversion of data types

int (2.33) returns 2

float (3) returns 3.0

str (53) returns the number 53 as a string

Expressions and operators, meaning in brackets

arithmetic

+ (plus), -(minus), * (times), / (divided by), ** (high), % (Modulo, remainder of a division)

16/3 returns 5 (integer division), 16.0 / 3 returns 5.333333333333333 (floating point number division)

Comparisons

==(equal), != (not equal),> (larger), <(smaller),> = (larger or equal), <= (smaller or equal)

logic

true (true), false (not correct), other (simultaneously), or (or), not (Not)

Element relationship

in (in the crowd), e.g. 3 in [1, 2, 3] (true), 4 not in [1, 2, 3] (true)

Strings

Strings can be used with + linked or with * be repeated, e.g.

"ABC"+“Def“ returns “abcdef“, 5*"A" delivers "AAAAA"

Sequences

Sequences are called tuples (1, 2, 3) and lists [1, 2, 3]. In contrast to dictionaries, sequences are ordered, i.e. each element has a unique position, starting with position 0 (Zero) for the first element of the list, -1 can be set for the last element, e.g. (3, 4, 5) [0] returns 3, (3, 4, 5) [- 1] returns 5

List Generators

range (10) equivalent to [0, 1, 2, 3, 4, 5, 6, 7, 8, 9], range (1.4) corresponds to [1,2,3]

Function definition

def square (x): return x ** 2square (3) returns 9

Commands for numbers and strings

round (a [, n]) - rounds a floating point number. Optionally, the number of decimal places can be specified, e.g.
round (5.59555, 2) returns 5.6

str () - convert to string, float () - convert to floating point number.

You can use not only numbers, but generally all objects str () convert to a string, e.g.
print(str(167) [- 1]) yields 7

len() - Determine the length of the string, e.g.

test_string = "Today"

len(test_string) returns 5

Control structures

if-elif-else                      Example:

x = 8 if x> 5: print ("x is greater than 5") elif x <5: print ("x is less than 5") else:      print ("x is 5" Output: x is greater than 5while               Example: i = 0 while i <4: print ("i is", i) i = i + 1 Output: i is 0 i is 1 i is 2 i is 3 for                Example:for i in range (10.21): print(i * i, end = '' 100 121 144 169 196 225 256 289 324 361 400 break,Example:continue and else for i in "Hello World!":if i == "":break print (i, end = '') Output: Hello

Modules

from ... import ... e.g. from math import * Importance: Everything (*) is imported from the math module.

Input and output

a = input (“Text“) #Entering the variable aprint “Text“, a # Output of text and value of the variable a

Example:

i = 99

print ('% 3d% 1.6f'% (i, 1.0 / i)

Output:

99   0.010101   

keywords

and, as, assert, break, class, continue, def, del, elif, else, except, exec, finally, for, from, global, if, import, in, is, lambda, not, or, pass, print, raise, return, try, while, with, yield

Program input

The program input is best done in a new Windows window (Ctrl + N) after calling IDLE (Python GUI).

  


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