- In python, there is no need to declare the variable type. A single variable name can store any of the data type.
- e.g. myvar = 1 , myvar = 3.24 , myvar = 'c' , myvar = "hello" .
- '+' operator can be either used to concatenate(in case of string type) or add(in case of int and float type).
- mixed variable type cannot be added.
- Lists are very similar to arrays. They can contain any type of variable, and they can contain as many variables as you wish. Lists can also be iterated over in a very simple manner
- List is declared in following manner - e.g. mylist = [];
- Listname.append(val) method is used to add a value to the end of the list.
- List methods can be accessed from here.
- Just as any other programming languages, the addition, subtraction, multiplication, and division operators can be used with numbers.
- "**" operator is used to raise the power of the first number by the second number.
- Lists can be concatenated using the "+" operator
- String or list can be printed, the desired number of times, by using the "**" operator.
- % is used to mark the place to print the desired value type format.
- for eg.
- print("hello!, %s " %str); //prints the value of str in place of the %s.
- In case u want to print several values at the desired places we use, %(all other data seperated by comma).
- Most of the print format is same as of C- language.
- String in python can be considered as a character array starting from index 0.
- All the string methods can be accessed from here.
- The if-else statement :
- General syntax follows - if condition : /body/ else : /body/
- We need not enclose the condition in parentheses.
- The if-elif-else statement : ---- elif as the name suggests is short of else if.
- BOOL value is True or False in python.
- "is" statement is a comparison statement. Unlike == , is statement matches the instance itself.
- "in" statement checks the presence of a variable in a list.
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The for loop :
- for eg.
- primes = [2, 3, 5, 7] for prime in primes: print(prime) // this code prints the values in the list.
- range() and xrange() in for loop provide for iterating over a certain range.
-
Prints out the numbers 0,1,2,3,4 for x in range(5): print(x)
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Prints out 3,4,5 for x in range(3, 6): print(x)
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Prints out 3,5,7 for x in range(3, 8, 2): print(x)
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- for eg.
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The while loop : It works the same as in any other programming language.
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"else" statement can also be used with for and while loops, only when they terminate within them, not with break statement.
- def keyword is used to define a function.
- We can create an object as a return value or can perform any printing actions.
- Object can be called an encapsulated entity of member functions and variables. These objects, instead of being created everytime, can be called as an instanece of class.
- Class can be defined as the collection of member functions and variables from which instances(objects) can be created.
- exempler code for better understanding of how to use class
- code:
{ // define the Vehicle class class Vehicle: name = "" kind = "car" color = "" value = 100.00 def description(self): desc_str = "%s is a %s %s worth $%.2f." % (self.name, self.color, self.kind, self.value) return desc_str //your code goes here car1 = Vehicle() car1.name = "Fer" car1.color = "red" car1.kind = "convertible" car1.value = 60000.00 //test code print(car1.description()) }
- code:
- A dictionary is a data type similar to arrays, but works with keys and values instead of indexes. Each value stored in a dictionary can be accessed using a key, which is any type of object (a string, a number, a list, etc.) instead of using its index to address it.
- for eg.
-
phonebook = {} phonebook["John"] = 938477566 phonebook["Jack"] = 938377264 phonebook["Jill"] = 947662781 print(phonebook)
After these, we need to move on to python libraries - numpy, matlplotlib, pandas etc,.
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