"Introduction to Python" is a fun and interactive Mozilla Study Group to share skills and ideas on how to get a head start to Python language. This group is best for beginners, yet it is open to all.
- Download Python interpreter on your computer.
Python is :
- General purpose programming language
- High-level programming language
- Easy to learn
- Multiple programming paradigms, including object-oriented, imperative, functional programming, and procedural styles.
- Interpreted language
- Fast
Before we get started let’s go through some basics for Python:
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Variable : It stores a piece of value/string, and is given a specific name. variable_name1 = 67 variable_name2 = "Taylor"
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Comments : For single line comment use #(pound), and for multiple line comment enclose whatever you want to comment in three quotes(''').
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Arithmetic Operators:
| Operators | Meaning |
|---|---|
| + | Addition |
| - | Subtraction |
| * | Multiplication |
| / | Division |
| ** | Exponential |
| % | Modulus |
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Comparators:
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Keywords : These are reserved words and cannot be used to name constants or variables or identifier name.
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print : print keyword is used to print anything like value/string on the console.
print("Test this on my screen!") -
String: Strings are derived data types. A string in Python is a sequence of characters. Strings are immutable. This means that once defined, they cannot be changed. However many python methods, can modify strings.
Some common string methods :-
stringVar.lower() - returns the stringVar in lowercase, like
str = "THIS IS AN EXAMPLE" print str.lower()This would give output as:
this is an example -
stringVar.upper() - returns the stringVar in uppercase, like,
str = "example" print str.upper()
This would give output as:
EXAMPLE -
stringVar.replace('a', 'b') - replaces all occurrences of a with b in the string, like
str = "Mary had a Cat. Cat was of Mary." print str.replace("Mary","Cat")
This would give output as:
Cat had a Mary.Mary was of Cat.-
len(stringVar) - returns length of the string
str = "Test the length"This would give output as:
15Alternative of this is,
stringVar.count() -
str(variableName) - This string method makes non-strings into strings,
str(56) ’56’ #Note that now 56 is a string not an integer
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String index : Each character is string is assigned an index number started with 0.
Assume, var_name = 'monkey'
Use following format to access the any character, var_name[index_number] like, var_name[4] for character 'e'
To access a group of characters, like 'onk', var_name[1:4]
- isalpha() : This function returns True, if all characters are string, else it returns False, if all characters are not string.
str = 'check'
print str.isalpha() # this would give output as True
str = 'this is not all…string'
print str.isalpha() # this would give output as False
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Module : It is a file that contains definitions, i.e. module can define functions, classes, and variables. Simply, it is a file consisting of Python code. Declared as
from module_name import function_name
For example, from math import sqrt
This command invokes ’sqrt’ function, which is included in 'math' module.
- In Python, whitespace is used to structure code. Whitespace is important, so you have to be careful with how you use it.
print('Hello World!')
####For Windows:
- Write python code on an editor like Notepad.
- Create a folder on your computer to use for your Python programs, such as C:\pythonpractice, and save your hello.py program in that folder.
- In the Start menu, select "Run...", and type in cmd. This will cause the Windows terminal to open.
- Type cd \pythonpractice to change directory to your pythonpractice folder, and hit Enter.
- Type hello.py to run your program!
** Note: If it didn't work, make sure your PATH contains the python directory. See Getting Python.*
####For Mac:
- Write python code on an editor like TextEditor.
- Create a folder on your computer to use for your Python programs. A good suggestion would be to name it pythonpractice and place it in your Home folder. Save your hello.py program into this folder.
- Open the Applications folder, go into the Utilities folder, and open the Terminal program.
- Type cd pythonpractice to change directory to your pythonpractice folder, and hit Enter.
- Type python ./hello.py to run your program!
####For Linux:
- Write python code on an editor like sublime.
- Create a folder on your computer to use for your Python programs, such as ~/pythonpractice, and save your hello.py program in that folder.
- Open up the terminal program.
- Type cd ~/pythonpractice to change directory to your pythonpractice folder, and hit Enter.
- Type python ./hello.py to run your program!
**Note : Otherwise, users can write code on any other IDE like PyCharm. **
These are used to perform different computations or actions depending on whether a condition evaluates to true or false (Please note that true and false are always written as True and False in Python).
* if some-condition:
#block code one
#block code two*
* if some-condition:
#block code one
#block code two
else:
#block code three *
* if some-condition:
#block code one
#block code two
elif some-condition: //elif is short for else if
#block code three
else:
#block code four *
Function is a block of code that can be reused to perform single,related action. It majorly includes the following components:
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Function block begins with the keyword def, followed by the function name and parentheses() and semicolon:.
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Any input parameter or argument should be placed within the parentheses. Yet, this is not compulsory.
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Then comes the body which describes the procedure the function carries out.
###Calling of function
Once the basic structure of a function is finalized, you can execute it by calling it from another function or directly from the Python prompt.
Syntax: # Basic structure of function def function_name(): Comments #Body of function
These functions are called anonymous because they are not declared in the standard manner by using the def keyword. Lambda functions can have any number of arguments but only one expression. The expression is evaluated and returned. Lambda functions can be used wherever function objects are required.
Syntax lambda[arg1,arg2,arg3,….argn]:expression
###Lists
List is like array. It is a collection of different data-type variables.
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To access element of list
list_name[index_number]
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To add elements, this would add at the end of the list
list_name.append(value)
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To insert data at a specific desired place in the list
list_name.insert(index_number,"element_to_be_added")
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To delete/remove elements of the lists
del list_name[index_number]
ORdel list_name //deletes entire list
ORlist_name.remove("element_to_be_removed")
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Some other methods that can be applied on the list:
Method | Functionality ---------|: -------------------- append() | Add an element to the end of the list extend() | Add all elements of a list to the another list insert() | Insert an item at the defined index remove() | Removes an item from the list pop() | Removes and returns an element at the given index clear() | Removes all items from the list index() | Returns the index of the first matched item count() | Returns the count of number of items passed as an argument sort() | Sort items in a list in ascending order reverse() | Reverse the order of items in the list copy() | Returns a shallow copy of the list
##Looping
###For Loop
For loop in Python is used to iterate over a sequence (list, tuple, string) or other iterable objects. Iterating over a sequence is called traversal.
Syntax for variable in sequence: #block-code
###While Loop
The while loop in Python is used to iterate over a block of code as long as the test expression (condition) is true. It is an alternative for 'for-loop'.
Syntax while condition: #execute block code1 else: #execute block code
If the while condition is True, execute block code1 is executed. Otherwise, else part is executed.
Happy Learning!
