Try my app Expense Manager @ google play and amazon store.

Saturday, March 25, 2017

Python Part2: Conditional statements, While loops, Strings and Range

Conditional statements

If expr:
     print("expr is true")

If expr:
     print("It's true")
else:
     print("its’s false")

Python provides the elif keyword to eliminate the need for nested if … else structure.

h = 5
if h > 5:
      print("greater than 5")
elif h < 2:
      print("less than 2")
else:
      print("between 2 and 5.")

While loops

# While loop 
 While expr: 
     print("loop while expr is true") 

# Do-while in python 
 While True: 
     If expr: 
          Break

Strings

  • Immutable sequence of Unicode codepoints.
    • Immutable mean when you construct a string you can't modify its content.
  • Strings with Newlines
    • Multiline strings
      • """ this is
      • Multiline string"""
    • Escape sequences
      • This is \nmultiline \nstring.
  • len(s) gives number of codepoints(characters).
  • The + operator can be used for string concatenation.
    • >>> "This" + "is" + "a" + "string"
    • Thisisastring
  • Strings are immutable, so the += operator re-binds the reference to a new object. 
  • Use sparingly, concatenation with + or += can cause performance degradation. 
  • Call the join() method on the separator string. 
    • >>> Numbers = ';'.join([1, 2, 3, 4]) 
    • '1;2;3;4' 
  • Use the split() to divide a string into a list. 
    • >>> Numbers.split(';') 
    • [1, 2, 3, 4] 
  • Without an argument, split() divides on whitespace.
  • Join()-ing on an empty separator is an important and fast way of concatenating a collection of strings. 
  • The partition() method divides a string into three around a separator: prefix, separator, suffix.
  • Tuple unpacking is useful to destructure the result.

Range

  • Arithmetic progression of integers. 
  • Stop value is one-past-the-end. 
    • >>> range(5) 
    • range(0, 5) 
  • Ranges are 'half open'-start is include but stop is not. 
    • >>> for I in range(5) 
    • print(I) 
    • 4
  • Stop value of a range used as start value of consecutive range. 
    • >>> list(range(5, 10)) 
    • [5, 6, 7, 8, 9] 
    • >>> list(range(10, 15)) 
    • [10, 11, 12, 13, 14] 
  • Optional third step value. 
    • >>> List(range(0, 10, 2)) 
    • [0, 2, 4, 6, 8] 
  • Range(stop) range(10) 
  • Range(start:stop) range(0, 10) 
  • Range(start:stop:step) range(0, 10, 2)

No comments:

Post a Comment

Follow by Email

Google+ Badge