Pogojni stavki Python izvajajo različne izračune ali operacije glede na to, ali je določen logični pogoj ovrednoten kot resničen ali napačen. V Pythonu se stavki IF ukvarjajo s pogojnimi stavki.
V tej vadnici se bomo naučili uporabljati pogojne stavke v Pythonu.
Kaj je izjava Python If?
Za sprejemanje odločitev uporabite stavek if v Pythonu. Ima telo ukazov, ki se izvede samo, ko je izpolnjen pogoj stavka if. Dodatni stavek else, ki vključuje nekaj navodil za stavek else, se zažene, če je pogoj if napačen.
Pythonov stavek if-else se uporablja, ko želite zadovoljiti en stavek, medtem ko je drugi napačen.
Python sintaksa stavka if:
if Statement else Statement
Koda
# Python program to execute if statement a, b = 6, 5 # Initializing the if condition if a > b: code = 'a is greater than b' print(code)
Izhod:
a is greater than b
Kako uporabiti pogoj else?
'Drugi pogoj' se običajno uporablja pri presojanju ene izjave na podlagi druge. Če je pogoj, omenjen v bloku kode if, napačen, bo tolmač izvedel blok kode else.
Koda
# Python program to execute if-else statement a, b = 6, 5 # Initializing the if-else condition if a <b: code="a is less than b" print(code) else: print('a is greater than b') < pre> <p> <strong>Output:</strong> </p> <pre> a is greater than b </pre> <h2>When the else Statement does not Work</h2> <p>There could be a lot of situations where your 'otherwise condition' doesn't produce the desired outcome. Due to a flaw in the program's logic, it will print the incorrect result. This typically occurs when there are more than two statements or conditions in a program.</p> <p>An illustration will make this notion easier for you to grasp.</p> <p>Since both variables, in this case, are identical (9, 9), the program's output that 'x is greater than y' is FALSE. This is because it evaluates the first condition, or the if expression in Python, then prints the next condition (the else statement) by default if the first condition fails. The following step will examine how to fix this mistake.</p> <p> <strong>Code</strong> </p> <pre> # Python program when else condition does not work a, b = 9, 9 # Initializing the if-else condition if a <b: code="a is less than b" else: print(code) < pre> <p> <strong>Output:</strong> </p> <pre> a is greater than b </pre> <h2>How to use the elif Condition?</h2> <p>We can employ the 'elif' clause to fix the issue caused by the 'else condition' made earlier. You can instruct the software to print the third condition or alternative when the first two conditions fail or are erroneous by using the 'elif' condition.</p> <p> <strong>Code</strong> </p> <pre> # Python program to show how to use elif condition a, b = 9, 9 # Initializing the if-else condition if a <b: code="a is less than b" elif a="=" b: else: print(code) < pre> <p> <strong>Output:</strong> </p> <pre> a is equal to b </pre> <h2>Python Nested if Statement</h2> <p>The following example demonstrates nested if Statement Python</p> <p> <strong>Code</strong> </p> <pre> # Python program to show the nested if-else conditions A = 100 B = 200 C = 300 # Initializing the if-else conditions if B > A: if B > C: print('B is the largest number') else: if A > B: if A > C: print('A is the largest number') elif C > A: if C > B: print('C is the largest number') else: print('All numbers are equal') if B % C == 0: if A % C == 0: print('C is a common factor of A and B') </pre> <p> <strong>Output:</strong> </p> <pre> C is the largest number </pre> <hr></b:></pre></b:></pre></b:> Ko stavek else ne deluje
Lahko pride do številnih situacij, ko vaše 'drugačno stanje' ne prinese želenega rezultata. Zaradi napake v logiki programa bo natisnil napačen rezultat. To se običajno zgodi, ko sta v programu več kot dva stavka ali pogoja.
Ilustracija vam bo olajšala razumevanje tega pojma.
Ker sta obe spremenljivki v tem primeru enaki (9, 9), je izhod programa, da je 'x večji od y', FALSE. To je zato, ker ovrednoti prvi pogoj ali izraz if v Pythonu, nato pa privzeto natisne naslednji pogoj (stavek else), če prvi pogoj ne uspe. V naslednjem koraku bomo preučili, kako popraviti to napako.
Koda
# Python program when else condition does not work a, b = 9, 9 # Initializing the if-else condition if a <b: code="a is less than b" else: print(code) < pre> <p> <strong>Output:</strong> </p> <pre> a is greater than b </pre> <h2>How to use the elif Condition?</h2> <p>We can employ the 'elif' clause to fix the issue caused by the 'else condition' made earlier. You can instruct the software to print the third condition or alternative when the first two conditions fail or are erroneous by using the 'elif' condition.</p> <p> <strong>Code</strong> </p> <pre> # Python program to show how to use elif condition a, b = 9, 9 # Initializing the if-else condition if a <b: code="a is less than b" elif a="=" b: else: print(code) < pre> <p> <strong>Output:</strong> </p> <pre> a is equal to b </pre> <h2>Python Nested if Statement</h2> <p>The following example demonstrates nested if Statement Python</p> <p> <strong>Code</strong> </p> <pre> # Python program to show the nested if-else conditions A = 100 B = 200 C = 300 # Initializing the if-else conditions if B > A: if B > C: print('B is the largest number') else: if A > B: if A > C: print('A is the largest number') elif C > A: if C > B: print('C is the largest number') else: print('All numbers are equal') if B % C == 0: if A % C == 0: print('C is a common factor of A and B') </pre> <p> <strong>Output:</strong> </p> <pre> C is the largest number </pre> <hr></b:></pre></b:>
Kako uporabljati pogoj elif?
Uporabimo lahko klavzulo 'elif', da odpravimo težavo, ki jo je povzročil prej postavljen 'pogoj else'. Programski opremi lahko naročite, naj natisne tretji pogoj ali alternativo, ko prva dva pogoja ne uspeta ali sta napačna, s pomočjo pogoja 'elif'.
Koda
# Python program to show how to use elif condition a, b = 9, 9 # Initializing the if-else condition if a <b: code="a is less than b" elif a="=" b: else: print(code) < pre> <p> <strong>Output:</strong> </p> <pre> a is equal to b </pre> <h2>Python Nested if Statement</h2> <p>The following example demonstrates nested if Statement Python</p> <p> <strong>Code</strong> </p> <pre> # Python program to show the nested if-else conditions A = 100 B = 200 C = 300 # Initializing the if-else conditions if B > A: if B > C: print('B is the largest number') else: if A > B: if A > C: print('A is the largest number') elif C > A: if C > B: print('C is the largest number') else: print('All numbers are equal') if B % C == 0: if A % C == 0: print('C is a common factor of A and B') </pre> <p> <strong>Output:</strong> </p> <pre> C is the largest number </pre> <hr></b:>
Izjava Python Nested if
Naslednji primer prikazuje ugnezdeni stavek if Python
Koda
# Python program to show the nested if-else conditions A = 100 B = 200 C = 300 # Initializing the if-else conditions if B > A: if B > C: print('B is the largest number') else: if A > B: if A > C: print('A is the largest number') elif C > A: if C > B: print('C is the largest number') else: print('All numbers are equal') if B % C == 0: if A % C == 0: print('C is a common factor of A and B')
Izhod:
C is the largest number