if __name__ == '__main__': # If file is not imported, this will be executed
main()$ python3 $ pip3 install <package-name> $ python3 <filename>.py $ time python3 <filename>.py import <filename>- Input
input("Input: ")- Output Python automatically points the cursor to a new line. We need not specify explicitly.
print("Output")In python, we need not specify the datatype of a variable. The interpreter interprets the value and assigns a suitabe datatype for that.
number = 0
org = "GitHub"In python, we do not write a block of code in a pair of paranthesis.
We write it after : followed by an indentation in the next line.
The conditional statements include if, if-else, nested if and so on...
x,y = 0,1
if x < y:
print("x is less than y")
else:
print("x is not less than y")Note that the colon (:) following is required.
Similarly, the nested if also works.
As other programming languages, we have
for loop
for i in range(5):
print(i)The range function starts off with 0 till the number(excluded).
while loop
i=0
while(i < 10):
print("{} is less than 10".format(i))
i += 1There are a few ways to format a string in Python.
- Using the
%operator Strings can be formatted using the % operator:
>>> foo = 'world'
>>> 'Hello %s' % foo
'Hello world'To subsitute multiple instances, wrap the right hand side in a Tuple:
>>> foo = 'James'
>>> bar = 'Nancy'
>>> 'Hi, my name is %s and this is %s' % (foo, bar)
'Hi, my name is James and this is Nancy'You can also do variable subsitutions with a dictionary:
>>> dict = { "name": "Mike", "country": "Canada" }
>>> 'I am %(name)s and I am from %(country)s' % dict
'I am Mike and I am from Canada'
.format()
Introduced in Python 3, but is available in Python 2.7+
>>> 'Hello {}'.format('world')
'Hello world'Similar to the above, subsitutions can be referred by name:
>>> 'Hi {name}, your total is ${total}'.format(name='Bob', total=5.50)
'Hi Bob, your total is $5.5'- f-Strings
Available in Python 3.6+. Works similar to the above, but is more powerful as arbitrary Python expressions can be embedded:
>>> a = 5
>>> b = 10
>>> f'Five plus ten is {a + b} and not {2 * (a + b)}.'
'Five plus ten is 15 and not 30.'# These are all inplace operations returns a None value
<list>.append(<ele>) # Add an element to the end of the list
<list>.sort() # Sorts the given list
<list>.pop([<ele>]) # Removes the last element if no argument else removes the element at the index given
<list>.clear() # Makes it an empty list
<list>.insert(<index>, <ele>) # Adds the element before the index
<list>.extend(<iterator>)
<list>.reverse() # Reverse a given list# These are not inplace operations and has a return value
<list>.copy() # Makes a shallow copy of the list
<list>.index(<ele>) # Returns the index of the given element
<list>.count(<ele>) # Returns the number of occurrences of the elementkey-value pairs.
<dict> = {'Google':100, 'Facebook':80, 'Apple':90}
<dict>['Amazon'] = 85 # Adding a key along with the value
# Accessing the dictionary
for key in <dict>:
print("{key} -> {x}".format(key=key, x=<dict>[key]))
<dict>.keys() # Print all the keys
<dict>.values() # Print all the values
len(<dict>) # Find the length of the dictionary
<dict>.pop(<key>) # Removes the item with the specified key name
<dict>.copy() # Make a copy of a dictionaryA dictionary can also contain many dictionaries, this is called nested dictionaries.
$ sudo pip3 install pandas # Installing pandas module in Ubuntuimport pandas as pd
<dataframe>.head([<n>]) # Display the first n rows of the Dataframe, default value is 5 rows
<dataframe>.tail([<n>]) # Display the last n rows of the Dataframe, default value is 5 rows
<dataframe>.info() # Gives some information like, row and column datatypes, non-null count, and memory usage
<dataframe>.describe() # Provides some descriptive statistics about the numerical rows in the dataframe$ sudo pip3 install nltk # Installing nltk module in Ubuntuimport nltk
# Before trying any function download the word list
nltk.download('punkt')
nltk.download('averaged_perceptron_tagger')An anagram is a word or phrase formed by rearranging the letters of a different word or phrase, typically using all the original letters exactly once.
from collections import Counter
def anagram(first, second):
return Counter(first) == Counter(second)
anagram("abcd3", "3acdb") # TrueThis snippet can be used to check the memory usage of an object.
import sys
variable = 30
print(sys.getsizeof(variable)) # 24This snippet can be used to print a string n times without having to use loops to do it.
n = 2
s ="Programming"
print(s * n) # ProgrammingProgrammingThis method chunks a list into smaller lists of a specified size.
def chunk(list, size):
return [list[i:i+size] for i in range(0,len(list), size)]This method gets vowels (‘a’, ‘e’, ‘i’, ‘o’, ‘u’) found in a string.
def get_vowels(string):
return [each for each in string if each in 'aeiou']
get_vowels('foobar') # ['o', 'o', 'a']
get_vowels('gym') # []This method takes in the name of file and content then write the content into the file. If the file doesn't exist then it creates the file.
def write_to_file(filename, content):
try:
with open(filename, "w+") as f:
f.write(content)
print("Written to file successfully.")
except Exception as e:
print("Failed to write to file with error: ")
print(e)