If statements in Python
Tags: python, beginners
Published: 2020-03-03 13:46:32

With <a href="https://python.org">Python</a> conditional statement or if statements, the condition (True or False) determines if to execute a code block or not.

The Python programming if statement is in the form of:

```python
    if the condition is determined:
        Execute the statement ......
    else:
        Execute the statement ......
```

If the condition is not True, the latter statement is executed. Else the other code is executed. Indention used to create code blocks. The else statement is optional. 

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## If statement example

The following specific examples:

```python
# 1: if the basic usage                                                                                                                                                                  

flag = False
name = 'python'
if name == 'python': # variable determines if condition True or False                                                                                        
    flag = True # flag is set to true conditions are satisfied                                                                                                                           
    print('welcome boss') # and the greeting message                                                                                                                                     
else:
    print("hello employee")
```

The output is:

```
>>> welcome boss
```

The condition of the if statement can have `>` (greater than), `>=` (greater than or equal), `<=` (less than or equal). For equality use `==`.

For a set of comparisons:

```python
    if Condition 1 is determined:
        Statement 1 is executed ......
    elif judgment condition 2:
        Execute the statement ...... 2
    elif judgment condition 3:
        Execute the statement 3 ......
    else:
        Execute the statement 4 ......
```

Examples are as follows:

```python
# 2: elif usage                                                                                                                                                                          

num = 5
if num == 3:
    print('boss')
elif num == 2:
    print('user')
elif num == 1:
    print('worker')
elif num <0: # output value is less than zero                                                                                                                                            
    print('error')
else:
    print('conditions met') # conditions are met                                                                                                                                         
```

The output is:

```
conditions met
```

Python does not support the switch statement, so multiple conditions can only be achieved with `elif`.
```python
# 3: plurality of condition statements

num = 9
if num >= 0 and num <= 10: # determines whether the value is between 0 and 10
    print('in range')

num = 10
if num < 0 or num > 10: # determines whether the value is less than 0 or greater than 10
    print('out of range')
else:
    print('in range')

num = 8
# Determines whether a value between 0 to 5 or 10 to 15
if (num >= 0 and num <= 5) or (num >= 10 and num <= 15):
    print('in range')
else:
    print('out of range')
```

**Related links:**
* <a href="https://gumroad.com/l/dcsp">Python book and exercises</a>
* <a href="https://pythonbasics.org/if-statements/">Python if statements</a>