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# Python2.x Python Conditional Statements\\ \\ Python conditional statements determine which block of code to execute based on the result (True or False) of one or more statements.\\ \\ You can get a simple understanding of the execution process of conditional statements through the following diagram:\\ \\ !(#)\\ \\ Python programming language specifies any non-zero and non-empty (null) value as true, and 0 or null as false.\\ \\ In Python programming, the `if` statement is used to control program execution. The basic form is:\\ \\ if Condition: Execute statements... else: Execute statements...\\ Where "Condition" (the condition) is true (non-zero), the subsequent statements are executed. The executed content can span multiple lines, distinguished by indentation to indicate the same scope.\\ \\ `else` is an optional statement. It can be executed when you want to run content when the condition is not met.\\ \\ GIF demonstration:\\ \\ !(#)\\ \\ Specific examples are as follows:\\ \\ ## Example\\ \\ #!/usr/bin/python# -*- coding: UTF-8 -*-# Example 1: Basic usage of if flag = False name = 'luren'if name == 'python': # Check if the variable is 'python' flag = True# Set flag to true if condition is met print'welcome boss'# And print welcome message else: print name# Print variable name if condition is not met\\ \\ The output is:\\ \\ luren# Output result\\ The condition in an `if` statement can use `>` (greater than), `=` (greater than or equal to), `<=` (less than or equal to) to represent its relationship.\\ \\ When there are multiple values to check, you can use the following form:\\ \\ if Condition 1: Execute statements 1... elif condition 2: Execute statement2...elif Condition3: Execute statements 3... else: Execute statements 4...\\ Example:\\ \\ ## Example\\ \\ #!/usr/bin/python# -*- coding: UTF-8 -*-# Example 2: Usage of elif num = 5 if num == 3: # Check the value of num print'boss'elif num == 2: print'user'elif num == 1: print'worker'elif num= 0 and num<= 10: # Check if value is between 0 and 10 print'hello'# Output: hello num = 10 if num10: # Check if value is less than 0 or greater than 10 print'hello'else: print'undefine'# Output: undefine num = 8# Check if value is between 0-5 or 10-15 if(num>= 0 and num= 10 and num` (greater than) and ` 0 ) and ( b / a > 2 ): print "yes"else : print "no"\\ However, the following code will cause an error:\\ \\ a=0 b=1if ( a > 0 ) or ( b / a > 2 ): print "yes"else : print "no"(javascript:;)Shenxian Clan\\ \\ a72***@qq.com 9 years ago (2017-05-20) \\ 2. #0 Tao\\ \\ num***10@163.com [](#)68 #!/usr/bin/env python# -*- coding: UTF-8 -*-# A simple conditional loop statement to implement the Tower of Hanoi problem def my_print(args): print args def move(n, a, b, c): my_print ((a, '-->', c)) if n==1 else (move(n-1,a,c,b) or move(1,a,b,c) or move(n-1,b,a,c)) move (3, 'a', 'b', 'c')\\ > For more Tower of Hanoi problems, see: [\\ \\ (javascript:;)Tao\\ \\ num***10@163.com 9 years ago (2017-07-03) \\ 3. #0 sherlockzak\\ \\ for***rpoetry@mail.com [](#)101 Python does not have a **switch/case** statement. When encountering many situations, writing many **if/else** statements is not easy to maintain. In this case, you can consider using dictionary mapping as an alternative:\\ \\ #!/usr/bin/env python# -*- coding: utf-8 -*-import os def zero(): return "zero"def one(): return "one"def two(): return "two"def num2Str(arg): switcher={ 0:zero, 1:one, 2:two, 3:lambda:"three" } func=switcher.get(arg,lambda:"nothing") return func()if __name__ == '__main__': print num2Str(0)(javascript:;)sherlockzak\\ \\ for***rpoetry@mail.com 8 years ago (2018-03-30) \\ 4. #0 John\\ \\ oyw***@126.com [](#)52 Simple conditional judgment with `if` in one line:\\ \\ #!/usr/bin/python# -*- coding: UTF-8 -*- a = [1,2,3] b = a if len(a) != 0 else ""print(b) c=[] d = c if len(c) != 0 else "c is an empty list"print(d)\\ The output is:\\ \\ [1, 2, 3] c is an empty list(javascript:;)John\\ \\ oyw***@126.com 8 years ago (2018-05-22) \\ 5. #0 Linlangyue\\ \\ z46***0448@gmail.com [](#)59 Move duplicate data in a list to the end and return the count of unique elements in the list:\\ \\ def deduplication(nums): # write your code here exist_nums = {} pointer = 0 for num in nums: if num not in exist_nums: exist_nums = True nums = num pointer += 1 return pointer print(deduplication([1,1,1,1,1,1,2,2,2,2,2,2,2,2]))(javascript:;)Linlangyue\\ \\ z46***0448@gmail.com 7 years ago (2019-07-13) \\ \\